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of  the 

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V 


HOUSEHOLD  CHEMISTRY 


FOR  THE  USE  OF 


STUDENTS  IN  HOUSEHOLD  ARTS 


BY 


HERMANN  T.  VULTE,  Ph.D.,  F.C.S. 

Assistant  Professor  of  Household  Chemistry  in 
Teachers  College,  Columbia  University 


EASTON,  PA. 
THE  CHEMICAL  PUBLISHING  COMPANY 

1915 


*  '  -  Q  9 

'  '*  (j  f*j 


COPYRIGHT,  1915,  BY  H.  T.  VULTE. 


PREFACE. 

This  book  is  presented  for  the  general  study  of  the 
subject  of  chemical  operations  in  the  household.  It  is 
designed  to  meet  the  needs  of  secondary  schools  and 
colleges.  For  the  former  purpose,  the  instructor  will 
find  it  possible  to  make  such  selection  of  material  as  will 
cover  the  field  of  work  broadly  in  a  semester.  A 
thorough  completion  of  the  course  indicated  in  the  book 
would  require  the  attention  of  the  college  student  for 
one  year.  It  is  highly  advisable  in  this  longer  course  that 
one  third  of  the  period  be  given  to  explanation  and 
discussion  of  the  topics  in  the  form  of  lectures.  In 
the  shorter  course  the  object  may  be  accomplished  by  the 
more  informal  conference  system. 

It  has  seemed  best  to  include  a  large  amount  of 
descriptive  matter  in  this  book,  which  was  not  a  feature 
of  former  editions. 

I  wish  to  express  my  great  indebtedness  to  my  as- 
sistants, Mrs.  Ellen  Beers  McGowan  and  Miss  Sadie  B. 
Vanderbilt,  for  vauable  assistance  and  advice  in  the  pre- 
paration of  this  volume. 

H.  T.  V. 

May,  1915. 


TABLE  OF  CONTENTS. 


CHAPTER  I. 

INTRODUCTORY. 

PA.GE 

Outline  of  Topics  in  Organic  Chemistry I 

CHAPTER  II. 

ATMOSPHERE  AND  VENTILATION. 
Composition  of  the  Air.     Properties  and  Uses  of  Constituents. 

Experiments.     Factors  in  Ventilation  ;  Methods  of 7 

CHAPTER  III. 

WATER. 

Physical  and  Chemical  Properties.  Classification  of  Drinking 
Waters.  Qualitative  Examination.  Purification  of  Water. 

Hard  and  Soft  Water.     Experiments   23 

CHAPTER  IV. 

METALS. 

Metals  and  Alloys.  Processes  of  Manufacture.  Physical  and 
Chemical  Properties.  Effect  of  Acids  and  Alkalies. 
Methods  of  Cleaning.  Experiments 43 

CHAPTER  V. 
GLASS,   POTTERY,   AND  PORCELAIN. 

Manufacture.     Properties.     Experiments 62 

CHAPTER  VI. 
FUELS. 

Classification.  Solid  Fuels  :  Nature  and  Properties.  Liquid 
Fuels:  Manufacture,  Nature  and  Properties.  Gases:  Manu- 
facture, Properties.  Experiments 67 

CHAPTER  VII. 

CARBOHYDRATES. 

Classification.  General  Properties.  Glucose.  Fructose. 
Galactose.  Sucrose.  Maltose.  Lactose.  Starch.  Dextrin. 
Glycogen.  Celluloses.  Experiments  and  Practical  Appli- 
cations    88 


CONTENTS  V 

CHAPTER  VIII. 

FRUITS  AND  FRUIT  JUICES.  PAGH 

Composition.      Analysis  of  a   Fruit.      Experiments  in  Jelly 

Making 124 

CHAPTER  IX. 

FATS. 
Formation    and     Occurrence.        Properties.       Experiments. 

Butter  ;  Specific  Tests 130 

CHAPTER  X. 
PROTEINS. 

Classification.  Occurrence.  Solubilities.  General  and 
Specific  Properties.  Hydrolysis.  Albumins  and  Globu- 
lins. Egg.  Gelatin.  Bone.  Muscle.  Beef  Extracts. 
Milk.  Cheese.  Experiments 141 

CHAPTER  XI. 

BAKING  POWDERS. 

Composition.     Comparison  and  Types.     Experiments. 170 

CHAPTER  XII. 

TEA,  COFFEE,  CHOCOLATE  AND  COCOA. 

Sources.  Constituents.  Methods  of  Preparation.  Experi- 
ments.    1 76 

CHAPTER  XIII. 
FERMENTS  AND  PRESERVATIVES. 

Yeast.  Lactic  Acid.  Acetic  Acid.  Butyric  Acid.  Experi- 
ments. Method  of  Food  Preservation.  Tests  for  Preser- 
vatives. Tests  for  Purity  of  Certain  Foods 183 

CHAPTER  XIV. 

DISINFECTANTS   AND  DISINFECTION. 

Physical  and  Chemical  Methods  of  Disinfection.  Antiseptics. 
Tests  for  Disinfectants. 195 


VI  CONTENTS 

CHAPTER  XV. 

CLEANING  AGENTS.  PAGE 

Classification.  Soaps  and  Soap  Powders.  Manufacture  of 
Soap.  Soap  Analysis.  Scouring  Powders.  Metal  Polishes. 
Tests  for  Cleaning  Agents.  Bleaches,  Grease  and  Stain. 
Removers.  Bluings.  Experiments 201 

CHAPTER  XVI. 

VOLUMETRIC  AND  GRAVIMETRIC  ANALYSIS. 
Normal  Solutions.  Preparation  of  Solutions.  Use  of  Indica- 
tors. Analysis  of  Vinegar,  Cream  of  Tartar,  Baking  Soda, 
Household  Ammonia.  Analysis  of  Soap  or  Soap  Powders. 
Cereal  Analysis.  Kjeldahl  Determination  of  Nitrogen. 
Estimation  of  Reducing  Sugar 215 

CHAPTER  XVII. 
REAGENTS. 

Methods  of  Preparation 228 

APPENDIX. 
Useful  Tables.     List  of  Apparatus 232 


CHAPTER  I. 


INTRODUCTORY. 

Courses  of  instruction  in  Household  Economics  group 
themselves  principally  about  foods  or  other  materials 
used  in  the  household,  most  of  which  are  of  so-called 
organic  origin.  Hence  some  fundamental  instruction  in 
the  nature  of  organic  compounds  is  necessary,  and  pre- 
ferably should  precede  a  course  in  household  chemistry, 
which  is  largely  an  applied  chemistry  of  the  carbon  com- 
pounds. Often,  however,  a  preliminary  course  in  organic 
chemistry  cannot  be  introduced  into  the  curriculum. 
For  that  reason,  an  outline  of  a  series  of  lessons  in  the 
chemistry  of  the  carbon  compounds  is  given  here,  de- 
signed to  be  presented  as  lectures  and  experiments  run- 
ning parallel  with  the  work  in  household  chemistry  and 
often  merging  into  it.  In  such  a  combined  course,  the 
outline  as  given  will  need  to  be  adopted  to  the  allowed 
time,  perhaps  to  the  exclusion  of  the  aromatic  com- 
pounds, and  it  may  be  necessary  to  perform  many  of  the 
experiments  as  demonstrations.  To  give  the  study  its 
proper  emphasis  and  value,  stress  should  be  placed  less 
upon  individual  than  upon  type  compounds,  and  upon 
their  inter-relation  and  properties,  always  with  a  view 
to  enriching  and  making  more  effective  the  practical 
knowledge  which  the  student  has  of  substances  met  in 
everyday  life. 

It  may  be  pointed  out,  in  addition,  that  a  recent  course 
in  general  chemistry  of  the  most  modern  type  should  be 


2  HOUSEHOLD   CHEMISTRY 

required  as  a  prerequisite  of  household  chemistry.  In 
such  a  course  the  subject  matter  should  be  so  selected 
that  the  material  handled  in  household  chemistry  shall 
not  be  entirely  unfamiliar.  For  example,  more  definite 
information  would  be  useful  with  regard  to  the  consti- 
tution and  properties  of  the  imported  metallic  elements, 
and  a  few  of  their  simple  compounds. 

Outline  of  Course  in  Organic  Chemistry. 

I.  ORIGINAL  AND  PRESENT   MEANING  OF   TERM    "OR- 

GANIC." 

Importance  of  organic  chemistry — Some  differences 
between  organic  and  inorganic  compounds — Organic 
chemistry  the  chemstry  of  carbon  compounds — The  car- 
bon atom :  its  valency ;  graphic  expression  of  valency ; 
tendency  to  combine  with  hydrogen. 

II.  CHAIN  HYDROCARBON. 

The  Methane,  Ethylene,  and  Acetylene  Series. 

Development  of  Series — Nomenclature — Common  for- 
mulae and  differential — Properties — Occurrence  of  im- 
portant members. 

Application  to  Gaseous  and  Liquid  Fuels. 

Experiments:  Preparation  of  Methane,  Ethylene  and 
Acetylene. 

Reaction  for  the  double  bond. 

III.  ISOMERISM   APPLIED  TO  THE  HYDROCARBONS. 

Nature  and  effect  of  isomerism. 

IV.  SATURATION  AND  UNSATURATION. 

Meaning  of — General   formation  of  substitution  and 


HOUSEHOLD   CHEMISTRY  3 

addition      products — Isomeric      forms — Formation      of 
iodoform  and  chloroform. 

Experiment:     Preparation   of    iodoform. 

V.  ALCOHOLS. 

Derivation  from  the  hydrocarbon  through  substitu- 
tion— relation  to  metallic  hydroxides — Nomenclature — 
General  physical  and  chemical  properties  and  reactions — 
Source  and  uses  of  important  alcohols — Isomeric  forms : 
primary,  secondary,  and  tertiary  alcohols — Unsaturated 
alcohols — Glycols  and  polyhydric  alcohols — Sulphur 
alcohols  or  mercaptans. 

Applications  to  liquid  fuels ;  to  carbohydrates ;  to  fats ; 
to  fermentation;  preservation  of  foods. 

Experiments:     Preparation   of   ethyl   alcohol. 

Detection  of  methyl  alcohol. 

VI.  ALDEHYDES  AND  KETONES. 

Formation  from  alcohols — Comparative  properties  and 
reactions — Name,  source,  and  uses  of  important  ex- 
amples. 

Application  to  carbohydrates;  preservatives;  flavoring 
extracts. 

Experiment:  Preparation  of  formaldehyde,  acetalde- 
hyde  and  acetone. 

Reduction  by  aldehydes,  such  as  the  Fehling's  re- 
action. 

VII.  FATTY  ACIDS. 

Formation  from  aldehydes — Nomenclature — General 
properties  and  reactions — Occurrence  and  properties  of 


4  HOUSEHOLD   CHEMISTRY 

important  examples — Unsaturated  acids:  occurrence  and 
characteristics. 

Application  to  fats  and  oils. 

Experiments:     Preparation  of   acetic  acid. 

Separation  of  a  fatty  acid  from  a  fat. 

Illustration  of  drying  and  non-drying  property. 

VIII.  SCHEMATIC  REVIEW  OF  INTERRELATION. 

Hydrocarbon  »-*  Substitution  »-»  Alcohol  •-*• 
Aldehyde  »-»>  Acid 

IX.  ESTERS. 

Formation  of  type  esters  reviewed — Waxes — Glyceryl 
esters  of  fatty  acids:  general  properties;  occurrence  and 
properties  of  important  fats  and  oils. 

Application  to  fats  and  oils. 

Experiments:     Decomposition  of  a  fat. 

Preparation  of  ethyl  acetate. 

X.  ETHERS. 

Formation — Analogy  to  metallic  oxides — Nomencla- 
ture— Important  example — Properties — Relation  of  ethers 
to  alcohols ;  of  thio  ethers  to  mercaptans. 

Application:     Ether  extraction  processes. 

XI.  OXIDATION  PRODUCTS  OF  GLYCOLS  AND  POLYHYDRIC 

ALCOHOLS. 

Hydroxyacids — Dicarboxylic  acids — Special  examples : 
Glycollic,  lactic,  sarcolactic,  oxalic,  succinic,  malic,  tar- 
taric,  citric,  aconitic. — Sources  and  properties. 

Application  to  milk;  to  muscle;  to  fruits  and  fruit 
juices. 


HOUSEHOLD    CHEMISTRY  5 

XII.  NITROGEN  COMPOUNDS. 

1.  Alky  I  Cyanides. 

Analogy  to  halogen  derivatives — Hydrolysis  of 
cyanides — Other  cyanogen  compounds:  properties  and 
uses  of — Prussian  blue  as  bluing. 

2.  Amines. 

Primary,  secondary  and  tertiary  amines — Quaternary 
ammonium  bases — Unsaturated  amines  and  related  com- 
pounds— Important  examples. 

3.  Amides. 

Structure  and  properties — Amides  of  dicarboxylic 
acids — Important  examples. 

4.  Amino  Acids. 

Formation — Nomenclature — Properties  and  reactions 
Important  examples — Synthesis  to  peptids — Relation  to 
proteins. 

5.  Proteins. 

General  composition,  properties,  etc. 

6.  Purin  Group. 

Purin  ring  and  substituted  purins — Adenin,  guanin, 
hypoxanthin,  xanthin  and  uric  acid;  caffein;  theo- 
bromine. — Pyrimidin  base. — Relation  to  nucleoproteins. 

XIII.  AROMATIC  COMPOUNDS. 

Benzene  ring — Homolgues — Benzene,  naphthalene  and 
anthracene:  source  and  importance — Benzene  derivatives 
analogous  to  those  of  the  straight  chain  series — Formation 
of  substitution  products;  phenols;  alcohols;  aldehydes; 
acids;  amino  compounds;  diazo  compounds;  leuco  com- 


6  HOUSEHOLD   CHEMISTRY 

pounds — Properties  and  commercial  importance  of  com- 
pounds— Dyes. 

Experiments :  Preparation  and  detection  of  benzalde- 
hyde  and  of  benzoic  acid. 

Detection  of  vanillin  and  saccharin  and  salicylic  acid. 

Preparation  of  aniline. 

Diazotizing  aniline. 

Coupling  diazos  and  phenols. 

Formation  of  leuco  compounds. 

Reduction  of  indigo  blue  and  subsequent  oxidation. 

Preparation  of  helianthin  and  eosin. 


CHAPTER  II. 


ATMOSPHERE  AND  VENTILATION. 
Probably  no  subject  so  important  to  life  as  the  air  we 
breathe  is  so  little  understood,  nor  is  there  any  other 
instance  of  so  many  evils  arising  from  ignorance.  A 
knowledge  of  the  relation  of  pure  air  to  health  and  ef- 
ficiency should  be  a  part  of  the  education  of  people  in 
general.  In  no  other  way  will  there  be  a  solution  of 
problems  of  ventilation  in  homes  and  public  buildings, 
or  of  sanitary  housing  in  large  cities,  and  the  stamping 
out  of  devastating  diseases.  A  fundamental  knowledge 
of  the  properties  and  functions  of  the  atmosphere,  and 
the  principles  of  ventilation,  is  therefore  all-important 
for  the  student  of  household  chemistry. 

Composition  of  the  Air. — Pure  air  is  not  a  compound 
of  definite  composition,  but  a  mixture  of  gases.  The 
two  most  important,  oxygen  and  nitrogen,  occur  in  the 
proportion  of  about  20  parts  of  the  former  to  79  of  the 
latter.  Other  essential  constituents  are  carbon  dioxide, 
which  in  pure  air  averages  in  amount  a  little  over  3 
parts  in  10,000,  or  0.03  per  cent,  to  0.04  per  cent.,  and 
aqueous  vapor.  Traces  of  argon,  krypton,  neon,  ozone, 
hydrogen,  ammonia,  nitrogen  acids,  nitrites  and  nitrates, 
helium,  and  several  other  substances  are  normally  found 
in  varying  amounts. 

In  addition  to  the  above,  there  are  always  present  in 
ordinary  air  many  substances  classed  as  impurities,  the 
kind  and  amount  varying  with  the  locality.  Dust  from 


8  HOUSEHOLD   CHEMISTRY 

the  soil  and  from  factory  operations  is  found  as  sus- 
pended matter,  together  with  micro-organisms,  pollen, 
plant  seeds,  and  soot.  Offensive  gases  may  contaminate 
the  air  of  manufacturing  centers,  but  they  are  usually 
more  disagreeable  than  dangerous.  The  air  of  cities 
contains  anywhere  from  100  to  5,000  times  the  amount 
of  dust  and  bacteria  that  is  found  in  country  air. 

Properties  and  Uses  of  Constituents. — Oxygen. — Oxy- 
gen is  the  life-supporting  element  for  all  animals  and 
plants.  Diluted  as  it  is  with  nitrogen,  the  oxygen  of 
the  air  is  in  the  condition  and  proportion  best  adapted 
to  sustain  most  forms  of  life.  In  materially  increased 
amount  it  is  a  poison  to  human  beings;  on  the  other 
hand,  life  cannot  exist  if  the  proportion  falls  to  four- 
fifths  of  the  normal,  or  16  per  cent,  instead  of  about 
20  per  cent. 

In  animal  organisms,  a  relatively  small  amount  of 
oxygen  is  concerned  in  the  process  of  respiration.  Of 
20.9  per  cent,  inhaled  by  human  beings,  16  per  cent,  is 
returned  in  the  exhaled  air,  together  with  about  4.4  per 
cent,  of  carbon  dioxide.  The  oxygen  used,  however,  in 
the  respiratory  exchange  suffices  to  supply  heat  and 
energy  to  the  body  by  means  of  oxidative  processes  in 
the  protoplasm  of  tissue  cells. 

Plants  require  oxygen  for  respiratory  and  other 
processes  as  animals  do.  Part  of  the  necessary  amount 
is  inhaled;  part  is  obtained  in  the  process  of  photo- 
synthesis, through  the  action  of  chlorophyll  and  sun- 
light. A  plant  lacking  in  chlorophyll,  such  as  a  mush- 


HOUSEHOLD   CHEMISTRY  9 

room,  absorbs  oxygen  directly  from  the  air;  green 
plants,  in  the  presence  of  sunlight,  build  up  carbohydrate 
material  in  their  cells  by  synthesizing  carbon  dioxide 
and  water,  and  in  the  operation  release  oxygen.  The 
cells  use  as  much  of  this  as  they  require;  the  excess  is 
returned  to  the  air.  It  is  estimated  that  an  acre  of 
woodland  withdraws  in  one  season  about  45^  tons  of 
carbon  dioxide  from  the  atmosphere,  and  returns  3^2 
tons  of  oxygen.*  In  darkness  the  chlorophyll  becomes 
inactive;  the  plant  then  takes  oxygen  from  the  air.  It 
is  probable  that  the  roots  absorb  oxygen  from  the  soil 
and  from  ground  water. 

Ozone. — Ozone  is  a  peculiar  form  of  oxygen  which 
exists  as  O3.  It  is  produced  from  O2  by  electrical 
discharge,  by  the  action  of  moist  air  on  phosphorus,  or 
by  several  chemical  reactions,  such  as  the  action  of  con- 
centrated sulphuric  acid  on  potassium  permanganate. 
Its  odor  is  noticed  around  static  electrical  machines  and 
during  thunderstorms.  Ozone  is.  a  powerful  oxidizing 
agent,  but  is  found  only  in  minute  quantities  in  ordinary 
air.  The  salubrity  of  the  air  in  evergreen  forests  is 
ascribed  to  ozone,  formed  as  a  product  of  the  slow  oxi- 
dation of  turpentine  and  similar  plant  products. 

Nitrogen. — Nitrogen  is  an  inert  gas;  it  does  not  burn 
nor  support  combustion,  and  its  chief  value  to  organ- 
isms is  in  the  form  of  compounds.  It  is  not  utilized  in 
human  respiration  except  as  a  diluent  of  oxygen.  In 
the  plant  world  certain  species  of  bacteria  such  as  the 
*  Harrington  :  Practical  Hygiene. 


IO  HOUSEHOLD    CHEMISTRY 

micro-organisms  found  in  the  root  nodules  of  some 
legumes,  carry  nitrogen  directly  to  the  pea,  bean  or 
clover.  How  far  other  plants  are  able  to  utilize  atmos- 
pheric nitrogen  is  a  question.  The  main  source  of  the 
organic  nitrogen  in  their  tissues  is  the  nitrogen  com- 
pounds in  the  soil  due  to  micro-organisms  and  ammonia 
and  nitrates  washed  down  by  the  rain. 

Carbon  Dioxide. — Carbon  dioxide  is  a  heavy  gas 
which  will  not  support  combustion  or  respiration.  It  is 
the  result  of  oxidation  processes,  either  in  respiration, 
fermentation,  the  burning  of  tons  of  fuel,  or  chemical 
action  in  the  soil.  Harrington  estimates  that 
5,000,000,000  tons  are  discharged  annually  into  the 
atmosphere.  The  amount  of  carbon  dioxide  in  the  air 
may  vary  from  two  parts  in  10,000,  or  0.02  per  cent,  in 
the  purest  air  to  30,  40  or  even  100  parts  in  bad  con- 
ditions of  overcrowding.  Only  in  greater  amount,  how- 
ever, such  as  was  found  in  the  Black  Hole  of  Calcutta, 
is  it  destructive  to  animal  life.  Undiluted,  it  causes  in- 
stant suffocation  by  spasmodically  closing  the  glottis. 

On  account  of  the  solubility  of  carbon  dioxide  in 
water,  considerable  amounts  are  taken  out  of  the  atmos- 
phere by  rain  and  go  to  form  carbonates  in  the  soil  or 
remain  as  carbon  dioxide  in  the  water. 

Aqueous  Vapor. — The  term  aqueous  vapor  is  mis- 
leading and  does  not  strictly  represent  the  gaseous  form 
in  which  the  water  in  question  exists  in  the  atmosphere. 
The  amount  of  aqueous  vapor  which  a  given  volume  of 
air  is  capable  of  holding  without  condensation  depends 


HOUSEHOLD   CHEMISTRY  II 

upon  the  temperature  of  the  air.  At  o°  C.,  a  cubic  meter 
of  air  is  saturated  if  it  contains  4.87  grams  of  moisture ; 
at  20°  C.  or  68°  F.  it  can  contain  17.157  grams,  and  at 
32°  C.  or  about  90°  F.  it  may  hold  30  grams.  It  follows 
that  a  precipitation  of  moisture  results  when  the  tem- 
perature of  vapor-laden  air  changes  from  a  higher  to  a 
lower  point.  The  temperature  at  which  moisture  is 
deposited  is  called  the  dew  point. 

The  rate  of  elimination  of  moisture  from  bodies  de- 
pends largely  on  the  amount  of  moisture  already  car- 
ried by  the  air.  When  air  is  saturated,  it  can  take  up  no 
more;  evaporation,  therefore,  cannot  occur,  and  the 
moisture  normally  given  off  by  the  human  body,  for  ex- 
ample, is  deposited  on  the  surface  of  the  skin.  This  most 
disagreeable  condition  of  stickiness  is  associated  with 
days  of  great  humidity  in  summer,  with  moist,  raw  days 
in  winter,  and  with  overheated  crowded  rooms. 

Humidity  is  measured  in  terms  relative  to  the  satura- 
tion point  of  the  atmosphere  at  any  given  temperature. 
A  relative  humidity  of  50  means  that  the  air  contains 
only  50  per  cent,  of  its  moisture-carrying  capacity  at  that 
temperature.  The  limits  of  comfort  are  generally  given 
as  between  40  and  75;  a  humidity  of  75  to  100  is  op- 
pressive to  man  but  beneficial  to  plants. 

The  relation  of  atmospheric  moisture  to  heat  is  most 
important.  Water  has  a  great  capacity  for  heat  and 
gives  it  up  slowly.  It  acts  therefore  as  an  equalizer  of 
the  sun's  heat  and  a  moderator  of  temperature.  In  semi- 
arid  and  desert  regions,  where  the  air  is  moisture-free, 
2 


12  HOUSEHOLD   CHEMISTRY 

and  at  high  altitudes  where  the  amount  of  vapor  is 
relatively  less,  extreme  heat  during  the  day  and  a  sudden 
fall  of  temperature  at  night  are  observed.  It  is  esti- 
mated that  the  absorptive  and  radiative  power  of  aqueous 
vapor  is  16,000  times  that  possessed  by  air. 

Dust. — The  relation  of  dust  to  aqueous  vapor  is  sig- 
nificant. Without  this  suspended  matter  in  the  air  there 
would  be  little  or  no  precipitation  of  moisture,  but  a 
constant  state  of  saturation  would  be  possible.  The 
particles  act  as  nuclei  round  which  vapor  condenses  as 
fog  or  rain.  In  large  manufacturing  cities  the  preva- 
lence of  soot  and  dust  in  the  air  accounts  for  frequent 
fogs.  Bacteria  cling  to  dust  particles  and  with  them  are 
washed  out  of  the  air  by  rain. 

General  Properties  of  the  Air. — Density. — The  density 
of  the  atmosphere  varies,  the  principal  factor  in  varia- 
tion being  altitude.  At  3^2  miles  elevation  it  is  only  one- 
half  as  dense  as  air  at  sea  level  and  therefore  exerts  one- 
half  the  pressure.  The  normal  pressure  of  the  atmos- 
phere at  sea  level  upon  each  square  inch  of  surface  is 
about  15  pounds,  but  this  pressure,  which  amounts  to 
30,000  pounds  on  the  average  body,  is  not  appreciated, 
since  it  is  exerted  equally  in  all  directions.  Air  pressure 
is  commonly  measured  by  the  height  of  the  column  of 
mercury  which  it  is  capable  of  supporting,  the  recording 
instrument  being  called  a  barometer.  A  normal  pressure 
at  sea  level,  exerted  on  the  mercury  at  the  base  of  the 
barometer  tube,  is  sufficient  to  raise  in  the  tube  a  column 


HOUSEHOLD   CHEMISTRY  13 

of  mercury  weighing   14.7  pounds.       This  is  called  a 
pressure  of  i  atmosphere. 

When  the  mercury  falls  in  the  barometer,  which  us- 
ually happens  before  a  storm,  it  is  evident  that  atmos- 
pheric pressure  has  become  less.  This  is  because  the 
air  at  such  times  probably  contains  more  than  a  normal 
amount  of  water  vapor,  which  is  lighter  than  air,  its 
density  being  9,  while  air  averages  14.5.  The  term 
heavy,  sometimes  used  to  describe  the  atmosphere  in  this 
connection,  is  contrary  to  fact.  A  further  explanation 
of  the  barometric  condition  is  found  in  the  fact  that  as 
different  portions  of  the  earth's  surface  become  un- 
equally heated,  the  warmer  areas  impart  corresponding 
heat  to  their  atmosphere.  This  causes  a  rising  and 
dilation  of  air  over  a  given  section,  the  heated  column 
overflowing  at  the  top  upon  the  cooler  surrounding  atmos- 
phere. Diminished  pressure  results  in  the  rarefied 
column,  with  consequent  expansion  and  a  fall  in  tem- 
perature, until  the  moisture-precipitation  point  is  reached, 
and  the  contained  vapor  of  the  air  is  condensed  as 
cloud  or  rain.  In  changing  from  the  vapor  to  the  liquid 
form  latent  heat  is  released,  which  increases  the  rare- 
faction, and  the  upward  movement  and  overflowing  of 
the  air  column  continue.  Thus  is  created  a  condition  of 
low  pressure  which  the  barometer  indicates,  while  in 
the  surrounding  areas  high  barometric  readings  will  be 
found.  The  rain  area  will  naturally  correspond  with 
the  area  of  low  pressure. 

Diffusion. — By  a  fortunate  provision  of  nature,  gases 


14  HOUSEHOLD   CHEMISTRY 

of  different  specific  gravities  do  not  lie  in  strata  when 
mixed,  but  diffuse  until  the  mass  is  of  uniform  com- 
position throughout.  If  it  were  otherwise,  a  layer  of 
carbon  dioxide,  which  is  a  heavy  gas,  would  blanket  the 
earth,  and  offensive  and  poisonous  gaseous  emanations 
would  make  most  localities  uninhabitable.  As  it  is,  all 
such  gases  diffuse  through  the  atmosphere  as  soon  as 
produced.  Stratification  of  the  air  is  not,  however,  en- 
tirely controlled  by  diffusion.  The  local  movements  of 
air  currents  caused  by  unequal  heating  operate  like  a 
motor  fan  and  are  a  most  potent  equalizing  influence. 

Heat  Capacity, — Air  has  a  considerable  capacity  for 
taking  up  heat,  which  is  utilized  in  hot  air  heating. 

Liquid  Air. — Air  can  be  liquefied  by  causing  it  to 
escape  slowly  from  tremendous  pressure,  so  that  much 
heat  is  absorbed  in  expansion.  The  temperature  of 
liquid  air  is  nearly  400°  below  zero  Fahrenheit.  In  this 
state  it  volatilizes  rapidly  at  room  temperature,  the  more 
volatile  nitrogen  being  given  off  first.  This  leaves  an 
available  source  of  oxygen,  which  is  utilized  in  filling 
oxygen  tanks.  Liquid  air  has  a  faint  blue  color. 

EXPERIMENTS  ON  AIR. 

1.  Presence  of  Oxygen.— Pour  an  inch  of  alkaline  pyrogallol 
into  a  short  broad  test-tube,  close  with  a  rubber  stopper,  invert 
and  mark  the  position  of  the  stopper  and  liquid  on  a  gum  label 
pasted  on  the  outside  of  the  tube,  shake  the  tube  well,  invert 
and  open  under  water,  mark  the  level  of  the  water  in  the  tube 
when  open,  and  explain  the  phenomenon. 

2.  Carbon    Dioxide. — Expose   a    few    drops    of    lime-water   or 
barium  hydroxide  on  a  slide  to  the  air  and  notice  that,  by  the 


HOUSEHOLD   CHEMISTRY  15 

end  of  the  lesson,  it  is  cloudy.    What  is  the  precipitate?    Write 
the  reaction. 

3.  Hydrogen  Sulphide. — Moisten  a  filter-paper  with  a  solution 
of  acetate  of  lead  and  expose  to  the  air  until  the  end  of  the 
lesson.     Notice  the   black   coloration   due  to   the   formation   of 
lead  sulphide.     This  test  works  well  in  gas-lit  rooms. 

4.  Aqueous  Vapor — Saturate  a  strip  of  paper  with  cobalt  chlor- 
ide or  iodide,  thoroughly  dry  and  expose  to  the  air  out  and  in 
doors ;  under  moist  conditions,  it  turns  pink. 

Weigh  a  small  watch-glass  containing  about  I  gram  of  fused 
calcium  chloride,  wait  about  2  hours  and  weigh  again.  Note 
the  increase  in  weight  largely  due  to  water. 

5.  Dew  Point — Take  the  temperature  of   the  room,  immerse 
the  thermometer  bulb  in  a  glass  of  water,  and  add  ice  little  by 
little  until  the  first  indication  of  moisture  is  seen  on  the  outside 
of  the  glass.     If  humidity  is  low,  add  salt  to  hasten  process. 
Note  the  thermometer  reading;  it  is  the  dew  point  of  the  air  in 
the  room. 

6.  Determination  of  Relative  Humidity. — Use  a  sling  or  whirl 
psychrometer    This  instrument  has  two  thermometers  fastened 
to  a  frame  which  can  be  whirled  in  the  hand.    The  bulb  of  one 
thermometer  is  covered  with  muslin  which  is  made  wet  at  the 
beginning  of  the  test.    As  the  instrument  is  whirled  evaporation 
around  this  bulb  reduces  the  recorded  temperature  until  the  dew 
point  is  about   reached,   that  is,   the  temperature   at  which   no 
further  elimination  of   moisture  takes   place,   but  condensation 
occurs.    When  the   wet  bulb   thermometer   registers   its   lowest 
point  the  reading  of  both  is  taken  and  the  dew  point  calculated. 
(See  Glaisher's  table.    Harrington:  Practical  Hygiene.) 

7.  Relation  of  Dust  to  Rain — Fit  a  2-liter  flask  with  a  rubber 
stopper  having  2  perforations.    Pass  2  pieces  of  glass  tubing 
through  these,  long  enough  to  extend  nearly  half  way  into  the 
body  of  the  flask.     Attach  pieces  of  rubber  tubing  fitted  with 
pinch-cocks  to  the  free  ends  of  the  glass  tubing  just  above  the 
stopper.     Put  in  the  flask  sufficient  water  to  a  little  more  than 


l6  HOUSEHOLD   CHEMISTRY 

fill  the  neck  when  the  flask  is  closed  and  inverted.  Keep  the 
flask  inverted  and  allow  the  confined  air  to  become  saturated 
with  aqueous  vapor.  Now  withdraw  some  of  the  air  in  the 
flask  by  suction  through  one  of  the  rubber  tubes.  The  decreased 
pressure  causes  a  fall  in  temperature  and  a  condensation  of 
moisture  as  haze  or  fine  rain  throughout  the  air  space  in  the 
flask.  At  this  point  introduce  air  through  the  rubber  tubing  to 
restore  the  original  pressure  and  the  mist  disappears.  Now  wash 
the  air  in  the  flask  with  the  contained  water  until  its  dust  content 
is  removed.  Repeat  the  experiment  and  note  that  no  rain  is 
produced  in  the  dust-free  air. 

8.  Atmospheric  Pressure. — Pour  2  inches  of  water  into  a  clean 
ordinary  half  gallon  can,  boil  vigorously  and  close  the  opening 
with  a  close  fitting  cork.  Remove  the  burner  and  when  cool  the 
can  will  collapse.  The  can  should  have  a  small  opening  and 
preferably  be  rectangular  in  shape. 

Ventilation. 

The  scope  of  this  book  prevents  a  detailed  discus- 
sion of  ventilation  and  ventilatory  systems.  In  fact  it  does 
not  seem  possible  at  present  to  make  definite  statements  in 
regard  to  standards  of  temperature  and  composition  of  air 
in  a  well- ventilated  room,  since  the  whole  subject  of  ven- 
tilation is  undergoing  revision.  Experts  disagree  as  to  the 
comparative  physiological  effects  of  the  constituents  of 
vitiated  air,  and  if  perfect  systems  of  ventilation  have 
been  devised,  they  are  not  in  general  use.  However, 
until  all  buildings  are  equipped  with  such  a  system  as  a 
matter  of  course,  a  few  facts  and  principles  should  be 
generally  known  and  brought  to  bear  on  the  ventilation 
of  rooms  under  individual  control. 

Effect  of  Heat  and  Humidity. — It  has  been  well  estab- 
lished that  the  main  factors  causing  discomfort  in 


HOUSEHOLD   CHEMISTRY  17 

poorly  ventilated  rooms  are  excessive  heat  and  humidity. 
With  increase  in  temperature,  due  perhaps  to  over- 
crowding, the  moisture  in  the  air  increases  proportion- 
ately toward  saturation  point.  Evaporation  from  the 
body  now  becomes  relatively  impossible.  But  at  a  tem- 
perature of  70°  F.  or  over  the  body  depends  upon  evap- 
oration of  perspiration  to  maintain  its  heat  equilibrium. 
The  danger  now  arises  that  the  checking  of  evaporation 
may  cause  the  cutaneous  blood  vessels  to  become  so 
congested  that  the  temperature  of  the  skin  is  raised  and 
heat  transfer  by  conduction  and  radiation  is  increased. 
This  occurs  at  the  expense  of  the  efficiency  of  the  other 
organs,  particularly  the  brain.  Headache,  dizziness,  and 
even  fever  may  result.  Relief  is  at  once  felt  in  such 
cases  if  evaporation  is  aided  by  setting  in  motion  the  air 
in  the  room.  If  this  cannot  be  done  by  bringing  in  free 
currents  of  outside  air,  electric  fans  answer  the  purpose. 

On  the  other  hand,  too  rapid  evaporation  of  water 
from  the  skin  and  air  passages  will  cause  discomfort. 
This  is  felt  in  the  dry  air  of  steam-heated  rooms.  The 
skin  becomes  too  dry,  the  cutaneous  nerves  are  irritated, 
and  the  effect  is  felt  by  the  central  nervous  system.  This 
trouble  may  be  obviated  by  the  evaporation  of  water 
from  a  dish  placed  on  the  radiator. 

The  relation   of  heat  and   humidity  to   efficiency   is 

clearly  pointed  out  in  an  article  on  Work  and  Weather* 

by  Dr.  Ellsworth  Huntington.    The  efficiency  curves  of 

over  500  wage  earners  in  Connecticut  were  studied  dur- 

*  Harper's  Monthly  Magazine,  Jan.  1915. 


1 8  HOUSEHOLD   CHEMISTRY 

ing  a  period  of  4  successive  years,  and  those  of  1,600 
students  at  West  Point  and  Annapolis,  for  periods  of 
2  and  6  years  respectively.  The  declination  in  amount 
of  work  done  is  greatest  at  two  periods  of  the  year — 
through  January  and  a  part  of  February,  when  windows 
are  kept  closed  and  indoor  conditions  of  temperature  and 
humidity  are  below  standard,  and  from  the  latter  part 
of  June  to  the  end  of  August.  In  the  summer  of  1911, 
part  of  which  was  the  hottest  in  100  years  in  the  locality 
where  the  observations  were  made,  the  efficiency  of  the 
operatives  dropped  astonishingly;  in  1913,  a  cool  sum- 
mer, there  was  very  little  lowering  of  the  curve. 

Carbon  Dioxide. — Contrary  to  former  belief,  carbon 
dioxide  in  the  largest  quantities  likely  to  occur  in  the 
air  of  a  room  has  little  to  do  with  the  feeling  of  dis- 
comfort. If  the  room  is  kept  cool,  the  increase  may  be 
up  to  20,  30,  or  even  40  times  the  normal  amount1  with- 
out appreciable  effect,  and  no  serious  physiological  dis- 
turbance results  until  the  carbon  dioxide  content  is 
raised  to  about  3  per  cent,  with  a  corresponding  lowering 
of  the  oxygen.  This  is  approximately  75  times  the 
amount  present  in  pure  air.  At  this  point  Dr.  Angus 
Smith  found  feebleness  of  circulation,  slowing  of  heart 
action,  and  quickened  respiration,  but  could  detect  no  in- 
convenience with  2  per  cent.  Pettenkofer  and  Voit  ex- 
perienced no  discomfort  after  long  exposure  to  air  con- 
taining i  per  cent,  of  carbon  dioxide.2 

1  Rideal :   Report  on   Hygienic  Value  of    Gas  and   Electric 
Lighting,  presented  before  Royal  Sanitary  Institute,  London,  1907. 
*  Education  :  London,  Feb.  1912. 


HOUSEHOLD   CHEMISTRY  If) 

An  adult  will  add  0.6  cubic  foot  of  carbon  dioxide  to  the 
air  in  I  hour.  Therefore  in  a  room  containing  3,000 
cubic  feet,  the  carbon  dioxide  will  increase  in  that  time 
0.2  cubic  foot  per  1,000,  or  0.2  part  per  10,000,  i.e., 
from  an  initial  amount  for  pure  air  of  0.04  per  cent., 
to  0.06  per  cent.,  which  is  the  limit  of  the  standard  of 
purity  generally  given.  Theoretically  the  air  of  such  a 
room  with  one  occupant  would  require  renewing  each 
hour,  but  fortunately  the  average  room,  not  being  air- 
tight, is  constantly  receiving  some  outside  air  through 
various  openings. 

"Crowd  Poisoning." — Dr.  Rideal  states  that  the  worst 
that  can  be  said  of  even  respiratory  carbon  dioxide  is 
that  it  is  often  found  in  bad  company.  Emanations 
of  a  poisonous  nature  given  off  in  breathing,  cause  the 
unpleasant  odors  noticeable  to  a  person  coming  into  an 
occupied  room  from  the  outside  air.  Disease  germs  are 
likely  to  be  present,  and  to  circulate  more  freely  if  dust 
is  in  the  air.  Moreover,  sharp  particles  of  dust  may 
have  an  irritating  or  lacerating  effect  on  eyes,  nose,  or 
lungs,  making  the  tissues  more  susceptible  to  the  entrance 
of  bacilli.  Tuberculosis  is  commonly  spread  in  this  way. 

Experiments  made  under  the  direction  of  C.  E.  A. 
Winslow,  chairman  of  the  New  York  State  Commission 
on  Ventilation  (1914),  show  the  effects  of  heat,  humidity, 
and  stale  air.  It  was  found  that  when  the  temperature 
of  the  room  was  raised  from  68°  to  75°,  the  pulse  and 
blood  pressure  were  affected,  and  the  amount  of  physical 
work  accomplished  fell  15  per  cent.  None  of  these  bad 


2O  HOUSEHOLD   CHEMISTRY 

effects  were  felt  if  the  room  was  kept  cool,  although  the 
air  was  allowed  to  become  stagnant  for  8  hours,  so  that 
the  carbon  dioxide  content  increased  to  about  20  times 
the  amount  in  pure  air.  A  marked  effect  of  this  stale  air 
on  the  subjects  was,  however,  loss  of  appetite,  although 
the  odors  accumulating  in  the  room  were  not  noticed  by 
them.  This  sub-conscious  result  was  proved  by  serving 
standard  meals  and  calculating  the  amount  eaten  after  a 
period  spent  in  fresh  air  and  in  stale  air. 

Methods  of  Ventilation. — Of  the  two  methods  of  ven- 
tilation— natural  and  mechanical — the  former  is  the  one 
which  must  be  depended  upon  in  ordinary  houses. 
Natural  ventilation  relies  upon  the  movement  of  air 
currents  caused  by  differences  in  temperature  and  grav- 
ity, and  the  force  of  wind — an  uncertain  agent.  It  takes 
into  account  the  fact  that  air  becomes  lighter  when 
heated,  and  rises.  Heated  50°  F.  above  the  outside  air, 
the  air  of  a  room  will  be  increased  one-tenth  in  bulk, 
since  it  expands  1/500  of  its  volume  for  every  degree 
Fahrenheit.  Consequently,  since  good  ventilation  re- 
quires a  constant  supply  of  pure  air  and  a  corresponding 
removal  of  foul  air,  there  should  be  an  inlet  and  an  outlet, 
the  latter  at  the  top  of  the  room  where  the  heated  air 
can  escape,  the  former  nearer  the  bottom,  where  the 
colder  air  entering  can  have  an  opportunity  of  circulat- 
ing through  the  room  and  pressing  the  warmer  air  up- 
ward. The  problem  of  ventilation  in  winter  often  be- 
comes a  question  of  draughts.  If  the  inlet  is  arranged 
so  that  the  air  may  pass  in  a  vertical  direction  over  the 


HOUSEHOLD   CHEMISTRY  21 

heads  of  the  occupants  of  the  room,  and  at  the  same 
time  be  somewhat  warmed,  this  trouble  is  remedied.  If 
the  opened  window  is  the  only  form  of  inlet  possible,  a 
direct  draught  can  be  prevented  by  placing  a  frame  in 
the  opening  covered  with  some  open  mesh  material  such 
as  cheesecloth. 

The  inlets  and  outlets  should  be  as  far  as  possible 
from  each  other,  so  that  air  will  not  pass  directly  from 
one  to  the  other  without  circulating.  An  outlet  should 
properly  have  the  motive  power  of  heat  or  an  exhaust, 
otherwise  it  may  become  an  inlet  for  cold  air.  The  wind 
acts  uncertainly  as  an  exhaust  at  times;  a  mechanical 
arrangement  is  more  dependable.  A  fireplace  is  a  de- 
sirable natural  outlet,  having  the  extra  motive  power  of 
heat. 

Heating  by  hot  air  is  favorable  to  a  good  scheme  of 
ventilation,  provided  (i)  that  a  steady  supply  of  pure 
air  from  outside  is  brought  in  to  be  heated  and  circulated 
through  the  flues;  (2)  that  an  outlet  for  foul  air  be 
provided  in  the  room. 

Stoves,  steam  and  hot  water  heating  systems  offer  little 
aid  to  ventilation.  On  the  contrary,  stoves  withdraw 
the  purer  air  near  the  floor  for  purposes  of  combustion. 
Careful  attention  to  ventilation  is  necessary  with  these 
methods  of  heating. 

Too  often  people  live  in  tight  shut  rooms  in  winter 
because  they  cannot  afford  loss  of  heat  by  ventilating 
openings.  The  injury  to  health  is  apparent  in  even  a  few 
weeks,  in  lessened  vitality,  susceptibility  to  colds,  and 


22  HOUSEHOLD   CHEMISTRY 

actual  disease.  In  such  cases  occasional  throwing  open 
of  windows  with  rapid  exercise  at  the  time  answers  the 
purpose  with  less  loss  of  heat.  If  one  can  become  accus- 
tomed to  free  circulation  without  draughts,  the  body  tone 
is  raised  so  that  less  heat  is  required  and  the  chances  of 
injury  on  exposure  are  lessened. 


CHAPTER  III. 


WATER. 

Water,  or  hydrogen  monoxide,  the  universal  solvent, 
was  believed  to  be  an  element  until  the  experimental  work 
of  Cavendish  showed  it  to  be  the  product  of  the  chemical 
union  of  hydrogen  and  oxygen.  The  proportions  in 
which  these  gases  combine  are  two  parts  of  H  to  one  of 
O  by  volume,  and  one  to  eight  by  weight. 

Physical  Properties. — Latent  Heat. — Water  exists  in 
three  states  without  change  of  composition:  as  a  gas 
(steam)  at  100° ;*  as  a  liquid  (water)  between  o°  and 
100°,  and  as  a  solid  (ice)  below  o°.  In  passing  from 
the  solid  to  the  liquid  state,  additional  energy  is  required 
for  increased  molecular  spacing  and  motion.  This  is 
obtained  in  the  form  of  heat  from  surrounding  objects, 
and  becomes  the  latent  heat  of  fusion.  The  amount  of 
heat  transformed  in  this  way  in  melting  I  gram  of 
ice  is  sufficient  to  raise  the  temperature  of  i  gram  of 
water  from  o°  to  80°,  or  80  calories.  Conversely,  when 
water  freezes,  80  calories  per  gram  are  released  and  ap- 
pear as  sensible  heat. 

Steam,  being  a  gas,  requires  more  energy  for  mole- 
cular spacing  and  motion.  To  change  I  gram  of  water 
at  100°  to  steam  at  100°  necessitates  approximately 
537  (536.6)  calories.  One  gram  of  steam,  therefore, 
contains  537  calories  plus  the  100  calories  of  the  boiling 

*  Unless  otherwise  stated,   the  centigrade  scale  is  used   in 
giving  thermometer  readings. 


24  HOUSEHOLD   CHEMISTRY 

water.    When  steam  at  100°  condenses  to  water  at  100° 
537  calories  are  given  up  as  heat. 

Specific  Heat. — The  capacity  of  water  for  heat  is  so 
great  that  it  is  taken  as  the  standard.  The  specific  heat 
of  water  is  expressed  as  i ;  that  of  most  other  substances 
in  fractions.  For  instance,  the  specific  heat  of  alumin- 
ium is  0.21,  which  means  that  the  amount  of  heat  winch 
will  raise  i  gram  of  aluminium  i°  will  raise  I  gram  of 
water  0.21°. 

Conductivity. — Pure  water  is  a  poor  conductor  of 
heat  and  electricity,  but  dissolved  matter  increases  its 
conductive  capacity. 

Boiling  and  Freezing  Points. — The  boiling  and  freez- 
ing points  of  pure  water  under  standard  atmospheric 
conditions  are  used  as  convenient  points  for  standard- 
izing thermometer  scales :  in  the  centigrade  o°-ioo° ;  in 
the  Fahrenheit  32°-2i2°  ;  in  the  Reaumur  o°-8o°.  An 
increase  in  atmospheric  pressure  raises  the  boiling  point, 
a  decrease  lowers  it.  Boiling  and  freezing  points  are 
also  affected  by  substances  in  solution.  Solutions  having 
increased  density  boil  at  a  higher  temperature  and  freeze 
at  a  lower  than  pure  water.  If  electrolytes  are  in  solu- 
tion the  increase  and  decrease  are  greater  than  in  the 
case  of  non-electrolytes.  For  example,  the  boiling  and 
freezing  points  of  a  solution  of  sodium  chloride  are 
higher  and  lower  respectively  than  those  of  an  equivalent 
solution  of  sugar. 

Density. — The  weight  of  i  cc.  of  water  at  its  point  of 
greatest  density,  4°,  is  i  gram.  This  is  taken  as  the 


HOUSEHOLD   CHEMISTRY  2$ 

standard  of  density,  and  is  used  as  the  unit  in  specific 
gravity  measurements  of  liquids  and  solids.  The 
Baume  hydrometer,  an  instrument  for  determining  the 
specific  gravity  of  liquids,  floats  at  the  mark  O  in  dis- 
tilled water  at  15.5°  or  60°  F. 

Compressibility  and  Expansion. — Water  in  the  liquid 
state  is  practically  incompressible.  It  is  calculated  that 
the  small  compressibility  of  water  causes  a  lowering  of 
the  surface  of  the  ocean  to  the  extent  of  600  feet  where 
the  depth  is  6  miles,  or  an  average  depression  for  the 
large  ocean  bodies  of  116  feet.  On  passing  toward  the 
solid  state,  water  contracts  until  it  reaches  4°,  its  point 
of  greatest  density.  Below  this  point  its  volume  in- 
creases, and  at  freezing  point,  o°,  there  is  a  sudden 
further  expansion  of  10  per  cent.  Consequently  water 
at  4°  is  heavier  than  at  o°,  a  provision  of  nature  which 
makes  it  impossible  for  large  bodies  of  water  to  freeze 
solid.  When  water  is  converted  into  steam  it  expands 
more  than  most  other  known  liquids.  The  expression 
"a  cubic  inch  of  water  makes  a  cubic  foot  of  steam"  is 
approximately  true. 

Chemical  Properties. — As  a  chemical  agent,  water  is 
extremely  potent.     It  acts  usually  as  a  solvent,  but  in 
many     cases     produces     profound     chemical     changes. 
Briefly,  the  action  of  water  may  be  classed  as  follows : 
Water  of  Solution. 
Water  of  Hydration. 
Water  of  Hydrolysis. 
Water    of   Solution. — When    any    solid    dissolves    in 


26  HOUSEHOLD   CHEMISTRY 

water,  loss  or  gain  of  heat  is  apparent,  but  on  evaporat- 
ing the  liquid  the  solid  reappears  in  the  original  form. 
With  acids,  bases  and  salts  there  is  electrolytic  dissocia- 
tion in  addition  to  solution. 

Water  of  Hydration. — On  partial  evaporation  of  the 
liquid,  the  soluble  substance  reappears  in  changed  form, 
containing  a  definite  amount  of  the  water  in  the  solid 
state.  This  is  known  as  water  of  hydration  or  crystal- 
lization. Familiar  examples  are  washing  soda,  Na2CO3, 
10  H2O;  alum,  K2A12  (SO4)4,  24  H2O;  borax,  Na2B4O7, 
10  H2O;  Glauber's  salt,  Na2SO4,  5  H2O,  and  copper 
sulphate,  CuSO4,  5  H2O. 

Water  of  Hydrolysis. — Complete  hydrolysis  is  a  change 
in  which  water  enters  a  substance  as  H  and  the  hydroxyl 
OH,  splitting  it  into  new  compounds  generally  simpler 
than  the  original  substance.  The  changes  which  food 
undergoes  in  the  processes  of  digestion  are  examples  of 
hydrolysis,  such  as  the  breaking  down  of  sucrose  into 
fructose  and  glucose: 

C12H,20U  +  H,0  —  20^,0.. 

The  solution  of  the  non-metallic  oxides  SO3,  N2O5  and 
P2Oa  is  another  example : 

SO3  +  H2O  -~  SO2(HO)2  or  H2SO4. 

N2O6  +  H2O  •—  2NO2HO  or  2HNO3. 

P205  +  3H20  -~  2PO(HO)3  or  2  H3PO4. 
or  the  solution  of  caustic  alkalies  and  slaking  lime : 

N^O  +  H2O  •—  2NaOH. 

CaO  +  H2O  —  Ca(OH)2. 


HOUSEHOLD   CHEMISTRY  27 

Applications. — Explain  the  principle  of  the  ice  box, 
the  fireless  cooker,  the  double  boiler,  the  vacuum  pan,  the 
digester  kettle,  the  unglazed  water  jar,  the  freezing  mix- 
ture of  ice  and  salt. 

Why  are  cranberry  bogs  flooded  in  winter,  or  tubs  of 
water  put  in  vegetable  cellars  or  under  orange  trees  on 
frosty  nights? 

Explain  the  effectiveness  of  steam  heating,  hot  water 
heating,  a  hot  water  bag. 

Why  is  salt  put  on  an  icy  sidewalk  in  winter  ? 

Why  is  a  scald  from  a  steam  burn  worse  than  one 
from  boiling  water? 

Why  does  water  boil  more  quickly  when  there  is  con- 
siderable water  vapor  in  the  atmosphere? 

How  does  adding  salt  to  the  water  in  boiling  vege- 
tables and  keeping  the  cover  on  the  dish  affect  the  boiling 
point  ? 

Why  is  a  mixture  of  ice  and  salt  more  effective  than 
ice  and  sugar  in  freezing  ice  cream? 

Explain  the  cooling  effect  of  perspiration. 

EXPERIMENTS  ON  WATER. 

1.  Heat  Conductivity — Fill  an  8-inch  test  tube  two-thirds  full 
of  water,  grasp  the  lower  end  of  the  tube  with  the  fingers  and 
hold  in  the  flame  at  a  slight  inclination  from  the  perpendicular. 
Note  that  the  upper  part  will  boil   before  the  lower  becomes 
uncomfortably  hot  to  hold.    Reverse  the  order  of  heating  and 
note  the  same  result.    Explain. 

2.  Boiling-Point    Under    Atmospheric    Pressure. — Pour    about 
250  cc.  of  distilled  water  into  a  half  liter  round  bottom  flask 
supported  on  a  ring  stand.     Introduce  a  thermometer  so  that  the 

3 


28  HOUSEHOLD   CHEMISTRY 

bulb  only  is  immersed  in  the  liquid  and  apply  heat.  Note  the 
point  to  which  the  mercury  rises  when  the  liquid  is  quietly  boil- 
ing, raise  the  thermometer  bulb  just  out  of  the  liquid  and  take 
the  reading.  Is  there  any  difference?  Does  the  thermometer 
indicate  any  higher  degree  of  heat  when  the  liquid  boils 
violently? 

3.  Boiling-Point  Under  Reduced  Pressure. — Select  a  cork  which 
fits  the  flask  tightly,  pierce  a  hole  through  it  and  insert  a  ther- 
mometer.   Now  half  fill  the  flask  with  water  and  boil  the  liquid. 
When  in  active  ebullition,  close  the  flask  with  the  cork  and  ther- 
mometer  and   instantly   withdraw   the   heat.    When   the   liquid 
ceases  to  boil,  read  the  thermometer,  and  grasping  the  neck  of 
the  flask  with  several  folds  of  a  towel,  hold  it  under  running 
cold  water.    What  happens  ?    Read  the  thermometer  and  explain. 

4.  Influence  of  Soluble  Matter — Note  the  boiling  point  of  a 
solution  of  10  grams  of  salt  in  100  cc.  of  distilled  water.    Ob- 
serving the  same  conditions  throughout,  repeat  the  experiment, 
using  sugar.     How  do  the  boiling  points   compare?     Explain. 
Cool  each  solution  to  15°  and  take  its  specific  gravity. 

5.  Take  the  specific  gravity  of  a  mixture  of  equal  volumes  of 
water  and  95  per  cent,  alcohol,  and  note  its  boiling  point.    Ex- 
plain. 

6.  Weigh  out  30  grams  of  table  salt,  measure  100  cc.  of  dis- 
tilled water,  and  use  only  as  much  of  the  water  as  is  required 
to  make  a  saturated   salt   solution    (pickle).    What  is   the   re- 
quired proportion  of  salt  to  water?    Take  the  specific  gravity 
of  the  solution  and  its  boiling  point,  and  compare  with  Experi- 
ment 4.    Will  a  fresh  egg  float  or  sink  in  this  liquid?    Evaporate 
a  few  drops  of  the  solution  on  a  microscope  slide  and  observe 
the  salt  crystals  under  a  low  power  lens. 

7.  Hydration  and  Hydrolysis — Take  a  tablespoonful  of  com- 
mon plaster,  mix  this  with  half  the  volume  of  water  in  a  porce- 
lain dish,  stirring  with  a  thermometer.    Record  the  result  and 
explain. 

8.  Slowly  pour  about  10  cc.  of  strong  sulphuric  acid  into  50  cc. 


HOUSEHOLD   CHEMISTRY 


of  cold  water,  stir  well  with  a  thermometer,  and  from  time  to 
time  record  the  temperature.    Explain. 

9.  Using  a  burette,  carefully  mix  exactly  52  volumes  of  alcohol 
(95  per  cent.)  and  48  volumes  of  water  in  a  100  cc.  stoppered 
cylinder.     How  many  volumes  result?     Explain. 

10.  Add  half  a  teaspoonful  of  dry  pulverized  lime   (CaO)   to 
an  equal  volume  of  cold  water,  stir  the  mixture  with  a  ther- 
mometer,   adding    more    water    if    necessary,    and    record    the 
thermometer  reading.     Explain  and  write  reaction. 

Water  may  be  made  to  show  the  path  of  travel  of  convection 
currents  as  follows : 

Fill  a  500  cc.  beaker  two-thirds  full  of  distilled  water,  place 
over  wire  gauze  on  a  ring  stand  and  apply  heat  by  placing  the 
Bunsen  burner  on  one  side  of  the  bottom.  When  the  water 
is  warm  drop  into  it  a  few  crystals  of  fuchsin  or  other  soluble 
coloring  matter  and  watch  the  path  of  the  crystals  through  the 
water. 

Potable  or  Drinking  Water. 

Classification  of  Natural  Waters. — Natural  waters  are 
never  pure,  as  they  dissolve  or  hold  in  suspension  gases, 
liquids,  and  solids  with  which  they  come  in  contact.  The 
following  is  a  convenient  classification: 

f  Rain        — Contains 
I  G  solved 

Atmospheric  1  and  gases  of  the  atmos- 

l  Fog  phere. 

Surface — Cloudy,     usually     a 
large  amount  of  suspended 
matter,    minimum    of    dis- 
Sweet  i      solved. 

Underground — Clear,    mini- 
mum  of  suspended  matter, 
maximum  of  dissolved. 
Salt      J  Brines — over  5  %  soluble  salts. 
Sea  water — 3.6^  solids. 
Mineral— excess    of    unusual 
mineral  matter  and  gases. 


Natural 
Waters 


very     little    dis- 
solids    but     dust 


Terrestrial 


3O  HOUSEHOLD   CHEMISTRY 

Potable  or  drinking  water  should  be  clear,  free  from 
odor  and  color,  and  should  contain  not  more  than  20 
grains  of  solids  per  U.  S.  gallon,  of  which  not  more 
than  one-half  is  organic  matter. 

The  soluble  mineral  matter  in  water  consists  of  a 
mixture  of  the  following  salts: 


Carbonates     ] 
Bicarbonates 
Sulphates 
Chlorides 


of 


Sodium 
Potassium 
Calcium 
Magnesium 


together  with  oxide  of  iron  and  silica  in  minute  amounts. 
An  excess  of  chlorides  may  be  due  to  sewage  or  animal 
contamination,  excess  of  lime  causes  hardness,  and  excess 
of  iron  usually  is  apparent  from  the  color  and  is  probably 
due  to  the  solvent  effect  of  organic  matter  in  the  water. 

On  boiling,  water  loses  its  dissolved  gases,  hence  dis- 
tilled or  sterilized  water  is  flat  or  stale. 

Qualitative  Examination  of  Water. — The  importance  of 
guarding  a  water  supply  from  contamination  is  evident. 
Equally  important  are  frequent  expert  analyses  of  the 
supply  in  order  to  be  sure  that  the  safeguards  used  are 
effective.  No  attempt  will  be  made  in  this  work  to  give 
methods  for  the  quantitative  estimation  of  the  impurities 
found  in  water.  However,  certain  qualitative  tests  may 
be  given  which  will  aid  in  detecting  such  impurities  when 
present  in  abnormal  amounts;  it  is  only  when  found  in 
such  amounts  that  the  water  is  open  to  suspicion.  The 
impurities  are  for  the  most  part  harmless  in  them- 
selves, but  if  found  demand  quantitative  analysis  and 


HOUSEHOLD   CHEMISTRY  3! 

possibly  bacteriological  examination.  A  thorough  in- 
vestigation of  the  surroundings  and  of  the  sources  of 
contamination  of  the  supply,  and  great  care  in  taking  the 
sample,  are  essential  in  making  an  examination  of  any 
water. 

The  tests  usually  made  are  with  regard  to  color  and 
appearance,  odor  and  taste,  and  for  the  presence  of  total 
solids,  free  and  albuminoid  ammonia,  nitrogen  as  nitrites 
and  nitrates,  chlorine,  temporary  and  permanent  hard- 
ness, and  sometimes  phosphates,  sulphates,  etc. 

The  color  and  turbidity,  odor  and  taste  of  a  drinking 
water  are  not  in  themselves  indications  of  its  purity,  but 
taken  with  other  data,  help  in  forming  an  opinion  of  the 
sample.  A  clear,  colorless,  tasteless  water  may  be  pol- 
luted ;  on  the  other  hand  a  safe  water  may  have  acquired 
color  from  dissolved  iron,  or  a  "peaty"  taste  from  swamp 
vegetation,  or  a  fishy  odor  from  the  decay  of  algae. 

Odor. — Rinse  a  stoppered  flask  with  the  water  to  be  tested, 
fill  it  two-thirds  full  of  the  sample,  oork,  shake  violently,  remove 
the  stopper  and  note  the  character  and  intensity  of  the  odor. 
Replace  the  cork,  warm  the  water  over  a  water  bath  to  40°, 
remove,  again  shake  thoroughly  observe  the  odor  as  before.  The 
odor  will  be  strengthened  by  heating.  A  putrid  or  offensive 
smell  probably  indicates  sewage  contamination. 

Color  and  Turbidity. — Fill  one  of  two  Nessler's  tubes  with  the 
water  under  test,  the  other  with  an  equal  volume  of  distilled 
water.  Compare  the  color  and  clearness  of  the  two  by  observing 
against  white  paper. 

Total  Solids. — This  is  a  method  of  determining  the 
total  residue  left  by  the  water  on  evaporation,  and  the 
proportion  of  mineral  and  organic  matter  present.  The 


32  HOUSEHOLD   CHEMISTRY 

following  experiment  gives  an  approximate  estimation1 
of  total  solids: 

1.  Weigh  a  clean  porcelain  dish,  measure  into  it  100  cc.2  of 
the  water  to  be  tested,  and  evaporate  to  dryness  over  a  water 
bath.    Cool  and  weigh.    The  increase  in  weight  gives  total  solids. 
Apply  gentle  heat  and  notice  any  charring  (due  to  organic  mat- 
ter).   A  sour  odor  at  this  point  indicates  sewage  contamination; 
a  peaty  odor,  the  presence  of  swamp  water.    Continue  heating 
until  the  residue  is  white  or  nearly  so ;  cool  and  weigh.    The 
loss  in  weight  represents  organic  matter,  the  residue  is  mineral 
matter.    Some  inaccuracy  must  be  expected,  due  to  the  action 
of  heat  in  volatilizing  carbonates  and  alkali  chlorides. 

2.  Concentrate  100  cc.  of  the  water  to  about  10  cc.,  cool  and 
test  for  mineral  matter  as  follows : 

(a)  Phosphates.  A  few  drops  of  the  liquid,  acidified  with 
HNO3,  is  added  to  a  larger  quantity  of  ammonium  molybdate  and 
heated  in  boiling  water.  A  yellow  crystalline  precipitate  indi- 
cates phosphates.  Phosphates  are  seldom  found  in  drinking 
water.  If  present  they  indicate  probable  sewage  contamination. 

(&)  Chlorides.  Add  a  drop  of  HNOs,  then  AgNCk  A  white 
precipitate  of  silver  chloride  soluble  in  NH«OH,  indicates  chlor- 
ides. 

(c)  Carbonates.  To  40  or  50  cc.  of  clear  lime  water  add  a 
small  amount  of  the  water  to  be  tested.  Any  cloudiness  soluble 
in  acetic  acid  shows  carbonates.  Make  the  flame  test.  A  yellow 
color  indicates  sodium;  a  violet,  potassium.  View  the  latter 
through  blue  glass. 

(rf)  Iron  as  ferric  compounds.  Slightly  acidify  with  HC1  and 
add  NH4SCN.  A  blood  red  color  indicates  iron.  Or,  to 

1  For  exact  methods,  see  Air,  Water  and  Food,  Richards  and 
Woodman,  and  Examination  of  Water  for  Sanitary  and  Technical 
Purposes,  I/effmann  and  Beam. 

2  If  100  cc.  are  evaporated,  the  residue  in  milligrams  repre- 
sents so  many  parts  per  100,000;  if  58  cc.  are  taken,  each  milli- 
gram of  residue  is  equivalent  to  a  grain  per  U.  S.  gallon. 


HOUSEHOLD    CHEMISTRY  33 

determine  the  oxidation  of  the  iron,  to  the  acidified  water  add 
K4Fe(CN)e.  A  dark  blue  color  indicates  ferric  salts.  With 
K3Fe(CN)6  a  blue  color  indicates  ferrous  compounds. 

(*)  Calcium.  Add  NH.C1,  NH,OH,  and  (NH^O*.  A 
white  crystalline  precipitate  of  calcium  oxalate  forms  on  boiling. 
If  calcium  is  present,  filter,  and  save  the  filtrate  for  (/). 

(/)  Magnesium.  To  the  above  cooled  filtrate  add  sodium 
phosphate.  Magnesium  shows  as  a  white  crystalline  precipitate 
of  ammonium  magnesium  phosphate. 

(g)  Aluminium.  Add  NfLCl  and  an  excess  of  NH4OH. 
Warm  the  solution.  A  white  flocculent  precipitate  of  aluminium 
hydroxide  appears  on  standing,  if  considerable  alum  is  present. 
The  logwood  test  (p.  174)  is  more  delicate  for  small  amounts. 

Free  and  Albuminoid  Ammonia. — Two  forms  of  am- 
monia are  looked  for  in  water — free  and  albuminoid. 
Neither  of  these  is  injurious  in  itself,  but  their  sig- 
nificance lies  in  the  fact  that  they  indicate  conditions 
favorable  for  pathogenic  bacteria.  The  free  or  ureal 
ammonia,  if  present  in  any  quantity,  is  considered  to 
show  recent  sewage  pollution  as,  although  it  is  found  in 
rain  water,  and  may  be  formed  by  the  decay  of  certain 
algae,  it  is  directly  associated  with  animal  excretions, 
e.  g.,  urea.  Urea  readily  yields  free  ammonia  as  fol- 
lows: 

(NHS)2CO  +  2H2O  —  (NH<)2CO3. 
(NH4),CO3  —  2NH3  +  H2O  +  CO2. 

Since  ammonium  carbonate  decomposes  as  above  on 
heating,  it  is  evident  that  free  ammonia  can  be  obtained 
by  simply  boiling  the  water. 

Albuminoid  ammonia  will  not  volatilize  by  this  treat- 
ment. When  present,  it  indicates  undecomposed  organic 


34  HOUSEHOLD    CHEMISTRY 

nitrogen,  generally  as  low  forms  of  plant  life.  It  is 
necessary  to  oxidize  these  substances  to  volatile  com- 
pounds before  this  form  of  ammonia  can  be  obtained  by 
distillation. 

Determination  of  Free  and  Albuminoid  Ammonia. — 
The  method  to  be  followed  is  distillation,  successive  dis- 
tillates to  be  obtained  and  tested  with  Nessler's  solution, 
which  gives  a  yellow  or  brown  color  in  the  presence  of 
ammonia. 

Directions. — Thoroughly  cleanse  and  rinse  with  distilled  water 
a  round  bottom  half  liter  flask  and  a  number  of  6-inch  test 
tubes.  Connect  the  flask  with  either  a  condenser  or  a  long  piece 
of  glass  tubing  arranged  to  deliver  into  the  receiving  test  tubes, 
which  in  this  case  must  be  cooled  by  running  water  or  ice.  Make 
all  connections  tight.  Fill  the  flask  about  two-thirds  full  of  the 
water  to  be  tested  and  distil  with  moderate  heat.  Collect  dis- 
tillates in  equal  amounts  in  successive  test  tubes,  about  25  cc. 
in  each,  and  add  to  each  the  same  number  of  drops  of  Nessler's 
solution.  Observe  any  deepening  of  color  by  looking  down 
through  the  tube  against  a  white  background.  The  color  may 
be  compared  with  standard  ammonia  solutions.  Continue  the 
distillation  until  a  sample  shows  no  added  color  with  Nessler's. 
Save  the  distillates  for  comparison  with  the  yield  of  albuminoid 
ammonia  in  the  following: 

To  the  balance  of  the  water  in  the  flask  add  alkaline  potassium 
permanganate  in  the  proportion  of  about  15  cc.  to  200  cc.  of 
water.  Distil  with  steady  moderate  heat,  collect  and  test  suc- 
cessive distillates  as  before  The  alkaline  permanganate  solution 
oxidizes  the  nitrogen  in  the  form  of  albuminoid  ammonia  to 
compounds  yielding  free  ammonia. 

Nitrites  and  Nitrates. — The  presence  of  nitrites  in 
water  is  supposed  to  be  due  either  to  the  incomplete 
nitrification  of  ammonia  or  to  the  reduction  by  micro- 


HOUSEHOLD    CHEMISTRY  35 

organisms  of  nitrates  already  formed.  While  traces  of 
both  may  occur  in  all  natural  waters,  a  large  quantity 
suggests  previous  pollution  by  nitrogenous  organic  mat- 
ter of  animal  origin.  This  material  begins  the  nitrogen 
cycle ;  by  decomposition  and  the  work  of  micro-organisms 
ammonia  compounds  follow,  and  these  in  turn  are 
oxidized  by  aerobic  organisms  to  nitrites.  Further 
oxidation  by  another  group  of  organisms  converts  these 
into  nitrates.  If  now  nitrates  come  within  reach  of 
chlorophyll  bearing  plants,  they  complete  the  cycle  by 
converting  the  oxidized  nitrogen  back  to  organic  nitrogen 
again.  The  importance  of  nitrite  and  nitrate  determina- 
tion in  studying  a  water  supply  is  evident. 

In  one  of  three  Nessler  tubes  put  100  cc.  of  nitrite-free  water 
(use  distilled),  in  another  the  same  amount  of  the  water  under 
test,  in  the  third  nitrite  water  (to  be  furnished  by  the  instructor). 
To  each  add  5  cc.  of  freshly  prepared  mixture  of  equal  parts  of 
sulphanilic  acid  dissolved  in  acetic  acid,  and  naphthylamine 
acetate  dissolved  in  dilute  acetic  acid.  Mix  and  allow  to  stand 
30  minutes.  If  the  solution  becomes  pink  the  water  contains 
nitrites. 

Chlorides. — Chlorine  is  found  mostly  as  sodium 
chloride,  although  other  chlorides  may  be  present.  The 
amount  of  sodium  chloride  in  any  given  water  supply  is 
affected  by  the  character  of  the  soil,  proximity  to  the 
ocean,  etc.,  but  it  should  be  constant  for  the  locality. 
Any  marked  increase  over  the  normal  figure  indicates 
sewage  contamination. 

Place  in  a  small  casserole  or  porcelain  dish  about  100  cc.  of 
the  water  to  be  tested,  and  in  another  dish  the  same  amount  of 
distilled  water.  Add  to  each  2  or  3  drops  of  potassium  chromate 


36  HOUSEHOLD   CHEMISTRY 

solution,  then  add  drop  by  drop  a  dilute  solution  of  silver  nitrate 
(N/io)  stirring  after  each  drop  until  a  faint  tinge  of  red  re- 
mains. Obtain  the  same  tint  in  each,  and  note  the  number  of 
drops  of  silver  nitrate  used  in  each  case.  Each  drop  of  silver 
nitrate  solution  is  equivalent  to  0.000293  gram  sodium  chloride. 

Oxygen  Consuming  Power. — This  is  a  method  of  esti- 
mating the  organic  matter  in  water  by  its  decolorizing 
power  in  the  presence  of  potassium  permanganate.  The 
test  is  not  especially  significant  even  when  performed 
quantitatively,  as  it  is  not  delicate  or  definite. 

Fill  two  clean  8-in.  test-tubes,  one  with  the  water  to  be  tested, 
the  other  with  distilled  water,  and  add  to  each  the  same  amount 
of  acidified  potassium  permanganate  solution.  Be  careful  not  to 
obtain  too  deep  a  shade  and  see  that  the  shades  match.  On 
standing  10  minutes,  there  should  be  an  appreciable  lightening 
in  color,  greatest  in  the  tube  of  water  under  test.  If  the  color 
entirely  disappears,  the  amount  of  organic  matter  is  probably 
dangerously  great.  Compare  with  the  test  under  total  solids. 

Ice  used  in  drinking  water  should  be  examined  as  to 
purity.  A  sample  should  be  melted  and  tested  by  the 
method  described  for  water. 

Water  Purification. 

Household  Methods.* — Boiling. — Boiling  is  the  simplest 
and  most  effective  household  method  of  making  a  drink- 
ing water  safe,  as  typhoid  and  other  pathogenic  bacteria 
are  killed.  Boiled  water  has  a  flat  taste  due  to  the  loss 
of  dissolved  gases,  but  this  can  be  remedied  by  aeration. 

Effect  of  Charcoal. — Charcoal  is  useful  as  a  decolor- 
izer  and  deodorizer. 

*  For  public  methods  of  water  purification,  see  Food  Indus- 
tries, Vulte"  and  Vanderbilt,  and  Our  Water  Supply,  Mason. 


HOUSEHOLD   CHEMISTRY  37 

To  50  cc.  of  water  add  enough  vinegar  to  give  it  a  distinct  but 
not  deep  yellow  color  then  divide  into  two  equal  parts.  Filter 
one  through  dry  freshly  ignited  boneblack  several  times  and 
compare  the  color  of  the  resulting  liquid  with  the  original 
solution. 

Effect  of  Alum. — Alum  readily  ionizes  in  water, 
forming  a  flocculent  precipitate  of  aluminium  hydroxide, 
which  collects  any  suspended  matter  and  removes  it  by 
sedimentation.  It  is  thus  useful  in  clearing  turbid  water 
for  laundry  purposes,  swimming  pools,  etc.,  and  is  used 
on  a  large  scale  in  some  filtration  beds. 

Take  any  sample  of  cloudy  or  slightly  colored  water,  even 
soapy  water  will  answer.  Add  a  very  small  quantity  of  finely 
powdered  alum,  shake  well,  filter,  and  compare  with  the  original 
sample.  Write  the  reaction  for  the  formation  of  aluminium 
hydroxide. 

Water  should  be  neutral  or  slightly  alkaline  to  work 
well  with  alum. 

Filtration. — Prove  by  the  following  experiment  the 
effect  ordinary  filtration  has  upon  substances  in  solution 
or  suspension  in  drinking  water: 

Filter  a  dilute  salt  solution;  taste  the  liquid.  Is  any  change 
produced?  Add  to  the  filtrate  a  few  drops  of  AgNOs,  shake 
well  and  filter  again.  Note  any  difference. 

Household  filters  of  the  Berkefeld,  Pasteur-Chamber- 
land  and  Aqua  Pura  types  are  effective,  as  they  remove 
micro-organisms  as  well  as  suspended  matter. 

Distillation. — This  is  an  effective  method  of  purifying 
water,  but  not  so  simple  for  household  practice  as  boiling. 
From  the  following  experiment  the  student  is  expected 
to  determine  the  effect  of  distillation  with  reference  to 
volatile  and  non-volatile  substances: 


38  HOUSEHOLD   CHEMISTRY 

Using  the  same  apparatus  as  for  the  determination  of  ammonia, 
distil  with  moderate  heat  a  solution  of  about  2  grams  of  copper 
sulphate  in  250  cc.  of  water.  Is  this  solution  acid?  Carefully 
examine  the  distillate  for  copper  sulphate.  Remove  the  burner, 
cool  the  apparatus,  and  add  5  cc.  of  ammonia,  shaking  well ;  a 
deep  blue  color  should  be  obtained  Distil  this  liquid  and  test 
the  distillate  as  before.  Explain. 

Hard  and  Soft  Water. 

With  reference  to  its  detergent  action,  two  kinds  of 
water  are  recognized — hard  and  soft.  Hard  waters  con- 
tain calcium  and  magnesium  salts  which  are  undesirable 
in  many  industries.  They  produce  the  troublesome 
boiler  scale,  they  are  a  serious  objection  in  sugar  refin- 
ing, and  in  many  textile  operations,  especially  in  dyeing. 
In  the  household  hard  water  makes  a  poor  detergent, 
because  soluble  calcium  and  magnesium  salts  form  in- 
soluble compounds  with  soap,  which  not  only  have  no. 
cleansing  value,  but  produce  a  troublesome  curd.  A 
certain  amount  of  soap  must  be  lost  in  this  way  before 
a  lather  will  form  and  cleansing  begin.  The  degree  of 
hardness  a  water  possesses  may  be  measured  by  its  soap- 
destroying  power.  The  total  hardness  of  most  water  is 
of  two  kinds — temporary  and  permanent. 

Temporary  Hardness. — This  form  is  caused  by  carbon- 
ates of  calcium  and  magnesium  held  in  solution  as  bi- 
carbonates  by  carbon  dioxide  present  in  the  water.  Boil- 
ing expels  the  CO2,  causing  a  precipitation  of  calcium 
and  magnesium  carbonates,  and  the  temporary  hardness 
is  removed.  Calcium  hydroxide  is  often  used  on  a  large 
scale  for  the  same  purpose.  Its  effect  can  be  shown  as 
follows : 


HOUSEHOLD  CHEMISTRY  39 

Pass  a  current  of  CO2  gas  into  a  small  amount  of  lime  water 
until  the  precipitate  clears.  What  was  the  precipitate?  What 
does  the  water  now  contain?  Write  the  reactions.  What  hap- 
pens if  more  lime  water  is  added?  Write  the  reaction,  and  show 
that  for  every  nine  parts  of  hardness  four  parts  of  Ca(OH)2 
are  required. 

Permanent  Hardness. — Permanent  hardness  is  due  to 
the  presence  of  calcium  sulphate  and  other  soluble  salts 
of  calcium  and  magnesium,  not  carbonates,  held  in  solu- 
tion by  the  solvent  action  of  the  water  itself.  Such  a 
water  cannot  be  affected  by  boiling,  but  may  be  soft- 
ened as  follows: 

1.  Prepare  a  hard  water  by  dissolving  o.i   gram  of  calcium 
sulphate  in  500  cc.  of  distilled  water.    Add  sodium  carbonate 
solution  to  a  portion,  and  note  the  result.     Write  the  reaction. 
Filter  and  save  the  nitrate. 

2.  Roughly  determine  the  amount  of  soap  solution  necessary 
to  make  a  lather  lasting  5  minutes  in  (a)   100  cc.  of  the  above 
filtrate,  and   (&)  an  equal  amount  of  the  untreated  hard  water. 
What  is  the  effect  of  the  Na2CO3? 

Quantitative  Estimation. — To  estimate  the  total  hard- 
ness of  a  given  water  the  procedure  may  be  as  follows : 

Make  a  standard  soap  solution  by  dissolving  10  grams  of  good 
castile  soap  in  sufficient  90  per  cent,  ethyl  alcohol  to  make  up  to 
I  liter.  For  use  mix  100  cc.  of  this  soap  solution  with  100  cc. 
of  distilled  water  and  30  cc.  of  95  per  cent,  alcohol. 

Put  58  cc.  of  the  water  under  test  in  a  clean  stoppered  8-ounce 
bottle,  add  the  soap  solution  >i  cc.  at  a  time,  shaking  thoroughly 
after  each  addition.  Continue  until  a  lather  is  formed  which 
will  cover  the  surface  of  the  liquid  when  the  bottle  is  placed 
on  its  side,  and  will  last  5  minutes.  Note  the  amount  of  soap 
solution  used. 


4O  HOUSEHOLD   CHEMISTRY 

Estimate  the  total  hardness  of  the  water  in  grains  per 
gallon  by  using  the  following  data : 

One  U.  S.  gallon  contains  58,318  grains,  58  cc.  contains 
58,000  milligrams.  Therefore,  58  cc.  represents  a  minia- 
ture U.  S.  gallon,  and  i  milligram  per  58  cc.  stands 
for  i  grain  per  gallon,  approximately.  One  cc.  of  the 
standard  soap  solution  is  the  equivalent  of  i  milligram 
of  Ca,  calculated  as  CaCO3. 

For  example,  if  10  cc.  of  soap  solution  are  used,  a 
gallon  of  the  sample  contains  10  grains  of  Ca,  spoken  of 
as  10°  of  hardness.  This  will  be  the  total  hardness  of 
the  water. 

To  estimate  the  temporary  hardness,  boil  58  cc.  of  the  sample 
for  i  or  2  minutes,  cool  to  the  temperature  of  the  unboiled  water, 
and  make  up  with  distilled  water  the  loss  by  evaporation.  Add 
the  soap  solution  as  before  and  note  the  amount  required,  now 
that  the  temporary  hardness  has  been  removed.  In  this  case 
the  permanent  hardness  has  been  overcome  by  the  soap  solution, 
and  the  difference  in  the  amounts  of  the  soap  solution  used  in 
the  two  cases  is  the  measure  of  the  temporary  hardness  of  the 
water. 

Use  of  Washing  Soda. — Washing  soda  is  cheaper  and 
more  efficient  than  soap  in  softening  hard  water.  The 
following  equations  show  the  ratio  of  efficiency  between 
the  two: 

(1)  CaSO4  +  Na2COs  «—  CaCO,  +  Na2SO4. 

136  106  • . • 

(2)  CaSO4  +  2C17H35COONa  -— 

136  612 

(CnHuCOO),Ca  +  Na2S04. 
Therefore  612  pounds  of  pure  soap  are  required  to  do 


HOUSEHOLD   CHEMISTRY  41 

the  work  which  106  pounds  of  washing  soda  will  do, 
making  a  ratio  of  6  :  I.  But  since  much  yellow  laundry 
soap  is  only  about  one  third  actual  soap,  the  balance 
being  resin,  water,  and  other  substances,  the  ratio  be- 
comes 18:  i,  and  in  actual  practice  i  pound  of  washing 
soda  is  considered  equivalent  to  1 8  or  20  pounds  of  soap. 
A  white  laundry  soap  of  good  quality  averages  about  75 
to  85  per  cent,  actual  soap. 

Problem. — A  water  contains  15  grains  (approximately 
i  gram  of  Ca  per  gallon.  How  much  of  Na2CO3,  white 
soap,  and  yellow  laundry  soap  will  be  required  to  over- 
come the  total  hardness  of  500  gallons?  Assume  that 
the  15  grains  of  calcium  are  in  the  form  of  calcium  sul- 
phate. 

For  exact  methods  of  hardness  determination,  see  Hehner's 
alkalimetric  method. 

Natural  soft  waters  are  usually  recommended  for  the 
laundry,  solely  because  they  are  lacking  in  soluble  lime 
and  magnesia  compounds  which  would  waste  soap.  But 
organic  matter  present  in  this  class  of  water,  through 
stagnation  or  from  soil  rich  in  humus,  dissolves  notable 
quantities  of  metallic  oxides  from  containers  and  con- 
duits, so  that  water  of  this  class  may  become  hard  from 
the  presence  of  soluble  organic  salts  of  such  elements  as 
iron,  lead,  copper,  tin,  zinc,  etc.  In  the  usual  hot  water 
supply  of  the  household  this  is  noticeably  the  case.  So 
that  a  moderately  hard  water — temporary  hardness  best 
for  the  cold  supply — which  will  deposit  insoluble  lime 
compounds  on  the  exposed  metallic  surfaces,  is  a  safe- 


42  HOUSEHOLD   CHEMISTRY 

guard.  Probably  the  ferrous  compounds  of  iron  are  the 
worst  to  deal  with,  as  they  usually  are  not  noticeable 
from  lack  of  strong  color,  but  readily  show  in  the  oxid- 
ized form  as  iron  rust  spots  after  drying  and  ironing 
white  garments.  If  iron  is  present  it  should  be  com- 
pletely removed,  either  by  long  boiling  and  settling  or 
filtering,  or  by  adding  washing  soda,  borax,  or  ammonia, 
then  boiling  and  settling.  Organic  matter  may  be  dis- 
closed by  the  permanganate  test.  If  present  in  consider- 
able quantity  it  would  be  well  to  oxidize  both  the  fer- 
rous compounds  and  the  organic  matter  by  means  of 
additional  permanganate  and  heat,  finally  settling  or  fil- 
tering, to  remove  any  residue. 


CHAPTER  IV. 


METALS. 

The  aim  of  this  chapter  is  the  study  of  the  physical 
and  chemical  properties  of  metals,  rather  than  of  their 
compounds,  especially  with  regard  to  their  use  in  the 
household.  Therefore  only  those  in  common  use  will 
be  considered.  Such  metals  are  iron  in  its  various  forms, 
nickel,  zinc,  copper,  aluminium,  silver,  lead,  tin  and  cer- 
tain alloys. 

Iron,  (Ferrum)  Fe,  occurs  in  nature  largely  in  the 
form  of  oxides:  haematite,  Fe2O3  (red),  and  magnetite, 
Fe3O4  (black),  the  latter  possessing  magnetic  qualities 
and  commonly  called  lodestone. 

The  metal  is  obtained  by  fusing  the  ore  in  shaft  fur- 
naces with  excess  of  carbon  and  enough  limestone  to 
furnish  a  fusible  ash  or  slag  with  the  silicious  matter 
present  in  the  ore.  The  following  equations  explain  the 
reduction  and  slagging: 

2Fe3O4  -f-  SCO  — »  3Fe2  +  8CO2. 

SiO2  +  CaO  —  CaSiO3. 

The  product,  "pig  iron,"  or  crude  cast  iron,  contains 
from  3-4  per  cent,  of  carbon  as  graphite  and  combined 
carbon  or  carbide  of  iron,  FesC,  rendering  the  mass 
fusible.  By  careful  smelting  in  small  shaft  furnaces 
called  "cupolas,"  the  pig  iron  is  obtained  in  the  form  of 
gray,  white  and  mottled  iron,  depending  on  the  rapidity 
of  cooling  the  moulds.  Pig  iron  frequently  contains 
small  amounts  of  impurities,  sulphur  and  phosphorus, 
4 


44  HOUSEHOLD   CHEMISTRY 

rendering  the  product  short  or  brittle,  while  hot  or  cold  ; 
during  the  refining  process  these  are  almost  entirely 
removed  in  the  slag. 

Cast  iron  is  brittle  and  hard,  it  melts  without  soften- 
ing at  1,200°  and  yields  a  thin  liquid  which  may  be  cast 
in  sand  moulds.  The  quality  of  the  product  depends 
largely  on  the  purity  of  the  iron  (freedom  from  S.  and 
P.),  its  temperature  of  cooling,  and  the  smoothness  of 
the  mould. 

Cast  iron  heats  more  slowly  but  retains  its  heat  better 
than  other  forms  of  the  metal,  hence  its  use  for  oven 
plates,  sad-irons,  stove  lids,  etc.  If  heated  repeatedly  to 
redness  in  presence  of  air  and  quickly  cooled  its  carbide 
content  increases  at  the  expense  of  the  graphite,  and  it 
becomes  whiter  and  more  brittle.  This  causes  the  fre- 
quent cracking  of  old  stove  lids.  Slow  cooling  allows 
less  carbide  to  form ;  as  a  result  the  lid  is  less  brittle,  less 
liable  to  crack,  and  has  a  darker  appearance.  On  the 
other  hand,  the  hardness  of  carbide  is  desirable  in  sad- 
irons, accordingly  they  are  frequently  heated  to  a  high 
temperature  and  plunged  into  cold  water.  Cast  iron  can 
be  made  harder  than  steel,  and  is  sometimes  used  for  the 
wheel  in  glass  cutters.  It  does  not  oxidize  as  readily  as 
steel  or  wrought  iron. 

Malleable  iron  is  intermediate  between  cast  and 
wrought  iron.  It  is  made  by  slowly  cooling  cast  iron  to 
increase  its  graphite  content  and  elasticity.  It  is  there- 
fore softer  and  less  brittle  than  ordinary  cast  iron,  and 
is  much  used  in  house  hardware. 


HOUSEHOLD    CHEMISTRY  45 

Wrought  iron  and  steel  are  prepared  from  pig  iron 
by  burning  out  part  of  the  carbon  in  hot  air  furnaces  of 
special  construction.  The  reverberatory  furnace  for 
producing  wrought  iron  is  really  a  large  oven  heated  by 
gas  and  provided  with  a  powerful  blast  of  hot  air. 
Liquid  pig  iron  is  run  on  to  the  hot  furnace  bed  where 
the  excess  of  oxygen  removes  the  carbon  as  follows: 
C2  -f  O2  — *  2CO.  As  the  CO  escapes  from  the  liquid 
mass  it  produces  a  bubbling  like  any  boiling  liquid. 
Gradually  as  the  carbon  is  burned  out,  the  iron  becomes 
pasty  or  semi-solid  and  is  collected  in  balls  with  large 
pokers  operated  by  hand  (puddling).  When  the  balls 
are  of  sufficient  size  they  are  removed  with  tongs, 
squeezed  to  remove  slag  and  rolled  into  short  bars 
(blooms  or  billets).  The  blooms  are  then  reheated  until 
soft  and  rolled  in  bars  and  rods ;  when  cold  the  bars  may 
be  drawn  down  through  steel  dies  into  wire  of  almost 
any  degree  of  fineness.  They  are  cold  forged  into  nails 
and  tacks.  Piano  wire,  the  purest  form  of  iron,  con- 
tains 99.7  per  cent.  Fe,  the  balance  is  mainly  carbon. 
Cold  wrought  iron  is  quite  soft,  bends  easily  and  has 
great  tensile  strength.  It  does  not  melt  readily  (1,600°) 
but  softens  on  heating  and  may  be  forged  and  welded. 

Steel  is  a  form  of  iron  between  cast  and  wrought, 
containing  1.5  per  cent,  carbon.  When  heated  and  slowly 
cooled  it  is  soft  (mild),  but  if  suddenly  cooled  is  harder 
than  glass.  Hardened  steel  cautiously  reheated,  may  be 
softened  to  any  desired  extent  (tempering).  At  a  high 
temperature  steel  melts  and  may  be  cast  like  iron. 


46  HOUSEHOLD   CHEMISTRY 

Two  kinds  of  steel  are  manufactured,  i.  e.,  Bessemer, 
the  cheaper  variety  used  for  rails,  plate  for  making  so- 
called  sheet  tin  and  galvanized  iron,  wire  nails,  etc., 
and  open  hearth  steel,  a  more  expensive  variety  used 
for  cutlery  and  tools. 

Bessemer  Process. — The  cast  iron  is  first  melted  in  a 
cupola,  and  then  run  into  a  special  furnace  (the  con- 
verter), where  a  powerful  blast  of  hot  air  bubbles 
through  the  molten  liquid  and  quickly  (15  minutes) 
burns  out  the  carbon  and  other  impurities  and  even  pro- 
duces some  oxide.  Just  at  this  point,  a  small  portion  of 
molten  cast  iron  containing  manganese  and  the  proper 
amount  of  carbon  is  added  and  the  mixture  immediately 
poured  into  the  moulds  and  cooled.  The  function  of  the 
manganese  is  to  assist  in  holding  the  carbon  in  solution. 

Open  Hearth  Method. — The  cast  iron  is  melted  in  a 
gas  furnace  with  dish-shaped  bed  together  with  scrap 
wrought  iron  and  iron  ore.  After  8  or  10  hours  heating, 
the  operation  is  complete  and  the  liquid  steel  is  drawn 
off  and  cast  in  ingots. 

Steel  rusts  much  more  readily  than  *  cast  iron  and 
usually  needs,  especially  if  polished,  a  protecting  coat 
of  oil.  Rust  may  be  removed  from  iron  or  steel  by  soak- 
ing in  kerosene  and  rubbing  with  fine  emery  or  carbor- 
undum and  oil,  but  stoves  and  sad-irons  should  not  be 
coated  with  kerosene  and  allowed  to  stand,  as  unsat- 
urated  compounds  in  the  hydrocarbon  take  up  oxygen 
and  cause  the  iron  to  rust. 

Galvanized  Iron. — See  zinc. 


HOUSEHOLD   CHEMISTRY  47 

Properties  of  Iron. — Iron  has  a  specific  gravity  of  7.8, 
and  when  pure  fuses  at  about  1800°.  It  is  strongly  at- 
tracted by  magnets.  In  moist  air  it  oxidizes  readily, 
forming  red  oxide  or  common  iron  rust,  Fe2O3.  This 
oxide  is  soft  and  friable  and  does  not  protect  the  metal 
from  further  action.  It  is  slightly  soluble  in  water, 
giving  it  a  characteristic  taste,  experienced  in  drinking 
water  conducted  by  iron  pipes.  The  other  type  of  oxide, 
Fe3O4,  is  formed  by  the  oxidation  of  hot  iron,  or  by  the 
action  of  superheated  steam  and  carbon  monoxide 
(Barff  Process).  Fe3O4  forms  a  dark  gray  adherent  but 
brittle  coat  and  protects  the  metal  from  further  action. 
It  is  called  the  magnetic  oxide  or  blacksmith's  scale. 
Russia  iron  is  sheet  iron  which  has  been  given  this  lus- 
trous protective  oxide  coat.  It  is  used  for  stovepipes,  etc. 
The  red  oxide  forms  the  basis  of  pigments  such  as  Ven- 
etian and  Tuscan  red. 

Iron  reacts  readily  with  warm  dilute  acids,  but  resists 
the  action  of  alkalies. 

EXPERIMENT. 

Boil  small  pieces  of  bright  and  rusty  iron  in  separate  test 
tubes  in  the  following  liquids:  Dilute  hydrochloric  acid  (1:1); 
20  per  cent,  acetic  acid,  and  10  per  cent,  caustic  soda  solution. 
Note  comparative  strength  of  action.  Filter  off  the  liquid  in 
each  case,  and  test  with  ammonium  thiocyanate  in  the  presence 
of  hydrochloric  acid.  A  blood  red  color  shows  iron  in  solution. 
Record  the  results.  Write  reaction  between  Fe2Cl6  and  NH4SCN. 

Nickel,  a  hard  white  metal,  occurs  in  the  pure  state 
only  in  meteorites,  but  is  found  combined  in  several 
minerals.  It  is  obtained  by  smelting  in  the  blast  fur- 


48  HOUSEHOLD   CHEMISTRY 

nace.  As  it  takes  a  high  polish  and  is  only  slightly  sus- 
ceptible to  oxidation  in  moist  air,  it  is  largely  used  as  a 
protective  and  decorative  coating  for  iron  and  copper. 
The  method  of  plating  nickel  on  iron  is  similar  to  silver 
plating.  The  bath  contains  ammoniacal  nickel  sulphate, 
(NH4)2SO4,NiSO4,6H2O,  in  which  the  article  to  be 
plated  is  suspended,  after  having  been  cleaned  by  acid. 
This  forms  the  cathode,  and  a  nickel  plate  the  anode. 

Nickel  plated  articles  should  always  be  cleaned  with 
a  mixture  of  diluted  ammonia  and  whiting,  or  rouge, 
and  polished  with  soft  cotton  waste. 

Nickel  has  a  specific  gravity  of  8.8,  and  a  melting  point 
of  I5oo°-i6oo°.  As  an  ingredient  of  alloys,  nickel  is 
found  in  German  silver  (nickel  I  part,  zinc  I  part,  cop- 
per 2  parts),  and  in  coin  nickel  (copper  3  parts,  nickel 

i). 

It  is  not  active  with  dilute  acids,  and  like  iron  resists 
the  action  of  alkalies. 

EXPERIMENT. 

Heat  small  pieces  of  pure  nickel  with  dilute  acids  and  alkalies 
as  under  iron  and  record  the  results.  Soluble  salts  of  nickel 
have  a  green  color  and  yield  a  black  precipitate,  NiS,  with 
ammonium  sulphide.  Neutralize  acid  solutions  with  NH4OH 
before  adding  (NH*)2S.  Write  reaction  between  NiClz  and 
(NH4)2S. 

Pure  nickel  utensils  are  valuable  in  the  household,  but 
the  initial  cost  is  comparatively  high.  In  the  laboratory 
they  form  a  desirable  substitute  for  iron. 

Zinc  occurs  chiefly  as  calamine  or  zinc  blende,  ZnCO3. 
After  calcination  to  drive  off  CO2,  the  oxide  is  mixed 


HOUSEHOLD   CHEMISTRY  49 

with  carbon  and  distilled  in  earthen  retorts  at  1,300- 
1,400°;  crude  metallic  zinc  "spelter"  condenses  in  the 
receivers  and  CO  burns  at  a  small  opening. 

ZnCOs  —»  ZnO  -f  CO2. 
2ZnO  +  C2  — •  2Zn  +  2CO. 

Zinc  is  bluish  white,  highly  crystalline  and  brittle  when 
cold.  By  heating  to  120-150°  and  rolling  under  hot 
rolls  it  remains  pliable  and  soft  on  cooling  (sheet  zinc). 
At  200-300°  it  becomes  brittle  again,  melts  at  433°  and 
boils  at  920°.  Its  specific  gravity  is  7. 

Zinc  burns  in  the  air  with  a  bluish  white  flame,  yield- 
ing a  white  oxide  which  is  the  base  of  the  pigment 
Chinese  white.  Zinc  oxide  is  a  common  ingredient  of 
face  creams  and  other  toilet  preparations. 

In  moist  air,  it  oxidizes  and  absorbs  CO2,  forming  a 
thin  adherent  coat  of  basic  carbonate  which  protects  the 
metal  from  further  change.  Dilute  acids  readily  dis- 
solve this  coating  and  thus  restore  the  original  brilliancy. 
Acids  and  alkalies  freely  attack  zinc,  liberating  hydrogen 
and  producing  soluble  compounds  which  are  poisonous, 
hence  zinc  vessels  should  never  be  used  for  the  prepara- 
tion or  storage  of  food.  Do  not  attempt  to  cleanse  zinc 
or  galvanized  iron  with  anything  but  neutral  soap  and 
hot  water. 

Sheet  zinc  is  frequently  used  for  roofs,  gutters,  cor- 
nices and  leaders  of  buildings;  but  does  not  last  well 
near  the  seashore,  on  account  of  the  salt  in  the  atmos- 
phere. 


5O  HOUSEHOLD   CHEMISTRY 

The  molten  metal  mixes  in  all  proportions  with  cop- 
per, tin  and  antimony.  See  German  silver,  brass,  etc. 

Zinc,  both  cast  and  rolled,  is  largely  used  in  primary 
batteries.  It  lasts  much  better  if  cleaned  with  dilute 
sulphuric  acid  and  coated  with  mercury  (amalgamated). 

EXPERIMENT. 

In  a  dilute  salt  solution  immerse  bright  strips  of  sheet  copper 
and  zinc  in  metallic  contact.  Prove  by  examination  of  the  liquid 
which  element  suffers  by  the  action.  If  zinc  is  in  the  solution, 
potassium  ferrocyanide  will  give  a  white  flocculent  precipitate 
of  zinc  ferrocyanide  in  acid  solution.  Test  for  copper  by  adding 
an  excess  of  ammonium  hydroxide;  a  blue  color  shows  its 
presence. 

Galvanized  iron  is  sheet  iron  or  steel  which  after  being 
cleaned  with  acid  is  dipped  in  molten  zinc.  It  is  prac- 
tically a  zinc  article,  resists  rust,  and  should  not  be  used 
as  a  receptacle  for  food. 

Copper. — Copper  (cuprum,1)  Cu,  is  found  native,  also 
as  sulphide  and  carbonate.  Native  copper  ore  is  crushed, 
washed  to  remove  rock  and  melted  with  flux.  The  metal 
usually  contains  a  small  amount  of  silver  which  is  re- 
moved by  electrolysis.  Carbonates  and  oxides  are  fused 
with  coal  to  reduce  the  metal.  Sulphide  ores  containing 
iron  require  complex  treatment;  in  Montana  the  pro- 
cedure is  as  follows :  Partial  oxidation  by  roasting,  and 
subsequent  fusion  in  Bessemer  converter  (with  silicious 
lining)  during  which  sand  and  air  are  blown  through  the 
molten  mass.  The  iron  is  oxidized  and  combines  with 

1  The  term  "  Cuprum  "  was  derived  from  the  island  of  Cyprus 
in  the  Mediterranean,  where  copper  was  first  mined  and  extracted. 


HOUSEHOLD   CHEMISTRY  51 

silica  forming  a  slag,  which  floats  on  the  copper.  Sul- 
phur, arsenic  and  lead  are  oxidized  and  volatilized. 

Copper  is  refined  by  electrolysis  in  the  following 
manner:  Thin  copper  sheets  coated  with  graphite  are 
suspended  in  tanks  of  copper  sulphate  solution  and  con- 
nected with  negative  pole  of  the  dynamo;  opposite 
are  heavy  plates  of  crude  copper  connected  with  the 
positive  pole.  Pure  copper  is  deposited  on  the  cathode, 
while  the  SO4  ionizes  the  anode.  The  impurities  not 
ionized  fall  to  the  bottom  of  the  tank. 

Properties. — Copper  is  a  red  metal  melting  at  1,057°. 
It  is  a  good  conductor  of  heat  and  electricity,  is  very 
malleable  and  ductile,  and  has  a  specific  gravity  of  8.9. 
Several  oxides  of  copper  are  known ;  two  important  ones 
are  the  black  or  cupric  oxide,  CuO,  and  the  red  or  cuprous 
oxide,  Cu2O.  The  latter  forms  slowly  in  dry  air;  in 
moist  air  green  basic  carbonate  (not  verdigris)  is  formed. 
Copper  utensils  are  often  lined  with  tin  to  prevent  the 
formation  of  this  coating.  When  free  from  oxide  cop- 
per resists  the  action  of  alkalies,  organic  acids  and  most 
mineral  acids,  and  is  much  in  demand  for  the  manu- 
facture of  apparatus  used  in  food  preparation,  e.  g., 
vacuum  pan  for  sugar,  milk,  etc.,  apparatus  for  canning 
and  preserving,  candy  making  and  beer  brewing.  Large 
hotels  and  restaurants  use  copper  cooking  utensils. 

The  most  important  alloys  of  copper  are: 

Brass,  containing 18-40%  Zn, 

Bronze,  containing 11%  Zn,  3-8%  Sn,  some  Pb, 

Gun  metal,  containing 10%  Sn, 

Bell  metal,  containing 25  %  Sn, 

German  silver,  containing 19-44 %  Zn,  6-22%  Ni. 


52  HOUSEHOLD   CHEMISTRY 

Brass  is  essentially  like  copper  in  its  properties. 

Metallic  copper  and  its  alloys  are  readily  cleaned  with 
dilute  oxalic  acid  or  ammonia.     In  the  laboratory  tar- 
nished copper  may  be  cleaned  as  follows: 
EXPERIMENTS. 

1.  Heat  a  piece  of  tarnished  copper  wire  in  the  upper  part  of 
the   Bunsen   flame.     Note   the   change    from   cuprous   to   cupric 
oxide.    When  the  wire  glows  drop  it  immediately  into  a  test 
tube  of  methyl  alcohol.    What  is  the  odor  observed?    Note  the 
appearance  of  the  copper.     Complete  the  reaction:    CH,OH  -\- 
CuO— * 

2.  Heat   small   pieces   of   clean   and   tarnished   copper   in   the 
reagents  described  in  experiment  i,  p.  47.     Finally  pour  off  the 
liquids  and  add  to  each  an  excess  of  ammonia;  a  blue  color 
shows  the  presence  of  copper.    Have  the  pieces  of  copper  been 
visibly  affected?    Write  the  reaction  between  CuCL  and  NH4OH. 

3.  Compare  the  heat  conductivity  of  copper  and  iron  by  hold- 
ing the  ends  of  copper  and  iron  wires  of  equal  length  and  size 
in  the  Bunsen  flame. 

Aluminium,  often  called  aluminum,  is  the  most  abun- 
dant of  the  elements,  with  the  exception  of  O  and  Si. 
It  is  not  found  in  the  metallic  state,  but  exists  as  sili- 
cates in  various  clays,  in  the  topaz,  garnets  and  feldspar; 
as  a  hydrated  phosphate  in  the  turquoise;  as  an  oxide 
in  corundum,  in  the  sapphire,  ruby,  emery,  etc.,  and  in 
bauxite,  from  which  it  is  prepared  commercially. 

The  method  of  preparation  consists  in  powdering  the 
bauxite,  freeing  it  from  water  and  organic  impurities, 
and  heating  it  with  caustic  soda  solution  under  high 
steam  pressure.  By  the  addition  of  alumina,  aluminium 
oxide  or  alumina  is  then  precipitated  from  the  product 
in  the  form  of  a  hydrate.  The  final  process  is  the  re- 


HOUSEHOLD    CHEMISTRY  53 

duction  of  alumina  by  electrolysis.  A  substance  called 
cryolite,  which  is  a  compound  of  aluminium,  sodium 
and  fluorine,  melts  at  a  low  temperature  and  easily  dis- 
solves alumina.  A  molten  mixture  of  the  two  is  con- 
nected with  one  terminal  of  an  electric  generator,  and 
the  current  is  introduced  into  the  mass  by  means  of  a 
number  of  carbon  rods  dipping  below  the  surface.  De- 
composition by  electrolysis  results,  and  the  aluminium 
collects  in  molten  form  at  the  bottom  of  the  mass,  from 
whence  it  is  drawn  off.  The  reaction  taking  place  is  usu- 
ally expressed  as: 

2A120S  +  3C  — >  4A1  +  3C02. 

Properties. — Aluminium  is  silver-white  in  color,  almost 
as  hard  and  tenacious  as  steel,  and  ranks  next  to  copper 
as  a  conductor  of  heat  and  electricity.  It  can  be  drawn 
to  extremely  fine  wire  and  beaten  to  a  film  1/400oo  °f  an 
inch  in  thickness.  A  film  of  oxide  which  forms  on  its 
surface  is  protective.  Its  specific  gravity  is  only  2.6,  and 
its  melting  point  600-70x3°. 

Aluminium  is  readily  reactive  with  alkalies  and  hy- 
drochloric acid,  and  slightly  so  with  organic  acids,  an 
action  which  is  increased  if  sodium  chloride  is  present 
or  if  the  metal  is  tarnished.  On  account  of  its  lightness 
it  is  much  in  demand  for  cooking  utensils,  but  care  must 
be  taken  that  it  does  not  come  in  contact  with  caustic 
alkalies.  It  discolors  readily,  and  should  be  cleaned  with 
a  neutral  scouring  powder,  or  neutral  soap  and  ammonia. 
Oxalic  acid  in  hot  dilute  solution  will  remove  any  dis- 


54  HOUSEHOLD   CHEMISTRY 

coloration  but  will  soon  roughen  the  surface  of  the 
metal. 

Several  alloys  of  aluminium  are  known,  the  principal 
ones  being  bronzes.  The  true  aluminium  bronzes  are 
compounds  of  Cu  and  Al  alone,  but  various  other  metals 
such  as  Zn,  Nii,  and  Mg,  are  also  introduced.  Aluminium 
has  been  added  to  brass  with  good  effect.  Other  alloys 
are  combinations  with  Fe,  Bi,  Sn  and  Ag.  Magnalium  is 
a  useful  alloy  containing  from  2  per  cent,  to  10  per  cent, 
of  magnesium.  It  takes  a  high  polish  and  works  well  in 
the  lathe. 

An  alloy  of  aluminium  and  copper,  called  cupror,  has 
been  placed  on  the  market  recently.  It  is  designed  to 
take  the  place  of  silver  for  flat  tableware,  trays,  bowls, 
pitchers,  etc.  The  color  of  the  alloy  is  that  of  i8-k  gold. 
The  properties  claimed  for  the  new  alloy  are  a  high 
degree  of  polish,  freedom  from  oxidation,  resistance  to 
acids,  durability  and  cheapness.  Articles  made  of  it 
cost  a  little  less  than  the  best  silver  plated  ware. 

Aluminium  is  of  two  forms  in  cooking  utensils:  cast, 
and  rolled  or  spun.  In  the  former,  copper  is  added  and 
the  utensil  is  cast  in  one  piece.  The  spun  articles  are 
made  from  sheets  of  aluminium  rolled  to  the  required 
thickness  and  drawn  to  the  desired  shape  on  a  machine. 

EXPERIMENT. 

Test  bright  and  tarnished  aluminum  as  in  experiment  i,  p. 
47.  Filter.  Neutralize  the  acid  solutions  with  ammonia  in  the 
presence  of  ammonium  chloride  and  the  alkaline  solutions  with 
HC1.  Note  the  precipitates  and  write  the  reactions. 

Silver  is  found  native  with  copper  and  gold,  and  also 


HOUSEHOLD   CHEMISTRY  55 

as  a  sulphide,  associated  chiefly  with  galena  (lead  sul- 
phide). Small  amounts  are  obtained  from  antimony  and 
arsenic  compounds,  and  in  the  form  of  silver  chloride. 

In  the  electrolytic  refining  of  copper  (p.  51)  silver  is 
separated  from  the  bath.  The  principal  methods  of  ex- 
tracting silver  from  its  ores  are  (i)  amalgamation;  (2) 
lixiviation;  (3)  smelting. 

In  the  amalgamation  process  the  chloride,  bromide, 
etc.,  are  brought  into  prolonged  contact  with  mercury, 
which  reduces  the  silver  from  its  compound  and  forms 
an  amalgam  with  it.  Complex  sulphides  of  silver  resist 
amalgamation  and  must  have  a  preliminary  treatment 
consisting  in  roasting  the  ore  with  common  salt  or  with 
copper  compounds  to  produce  silver  chloride.  This  was 
the  patio  process  used  in  Mexico  for  350  years,  and  only 
recently  superseded  by  the  cyanide  process,  described 
under  lixiviation. 

In  the  lixiviation  processes  the  silver  is  dissolved 
from  its  ores  by  aqueous  solutions  and  is  precipitated  as 
the  metal  or  as  a  sulphide.  The  cyanide  method  is  the 
most  important.  It  is  a  complicated  process.  In  brief, 
the  ore  is  crushed  fine,  mixed  with  cyanide  solution,  and 
the  pulp  kept  in  contact  with  the  solution  until  the  dis- 
solution of  the  silver  is  complete.  The  mass  then  passes 
into  vacuum  filters,  and  silver  is  precipitated  from  the 
clear  filtrate  by  either  zinc  dust  or  zinc  shavings.  Smelt- 
ing with  nitre  follows.  The  silver  thus  produced  is  im- 
pure, and  is  carried  through  a  refining  process. 

Smelting  is  a  process  applied  to  silver  ores  containing 


56  HOUSEHOLD   CHEMISTRY 

large  percentages  of  lead  and  copper.  From  the  blast 
furnace  the  silver  comes  out  associated  with  lead  as  pig 
lead  or  "base  bullion."  The  amount  of  silver  is  seldom 
over  2  per  cent.  It  is  separated  from  the  lead  by  the 
process  of  zinc  desilverization  and  cupellation.  Zinc 
and  lead  are  quite  insoluble  in  each  other  and  silver  is 
more  soluble  in  zinc  than  in  lead.  Taking  advantage  of 
these  facts,  the  process  is  operated  as  follows :  silver  lead 
is  melted  in  large  cast  iron  kettles  and  the  zinc  added  and 
well  stirred.  On  standing  and  partially  cooling,  the  zinc, 
carrying  silver  and  a  little  lead,  rises  and  forms  a  crust 
which  is  skimmed  and  heated  in  retorts  to  drive  off  zinc. 
The  residue,  lead  and  silver,  is  then  heated  in  a  rever- 
beratory  furnace  (cupellation)  with  bone  ash  bed.  The 
lead  oxidizes,  melts  and  is  absorbed  by  the  bone  ash, 
leaving  the  silver. 

Properties. — Silver  is  a  white  metal,  softer  than  copper 
and  harder  than  gold.  It  is  highly  ductile  and  malleable, 
and  the  best  conductor  known  of  heat  and  electricity. 
Its  specific  gravity  when  cast  is  10.5,  and  its  melting 
point  about  960°.  It  does  not  oxidize  readily  in  air,  but 
is  rapidly  attacked  by  sulphides,  producing  a  black  coat- 
ing of  Ag2S. 

Oxidized  silver  is  made  by  dipping  silver  articles  in  a 
solution  of  potassium  hydrogen  sulphide,  which  pro- 
duces a  film  of  silver  sulphide. 

Silver  dissolves  readily  in  nitric  acid,  is  somewhat  re- 
active with  most  other  mineral  and  organic  acids,  but 
not  at  all  with  alkalies. 


HOUSEHOLD    CHEMISTRY  57 

In  order  to  harden  silver,  it  is  alloyed  with  copper  in 
the  following  proportions:  coin  silver,  900  parts  silver, 
100  parts  copper,  sterling  silver,  925  parts  silver,  75  parts 
copper.  All  solid  household  silver  is  now  "sterling." 

Many  silver  ornaments  contain  even  less  silver,  but 
articles  stamped  "sterling"  are  trustworthy.  Silver 
plated  ware  consists  of  articles  fashioned  of  German 
silver  or  pewter,  on  which  is  deposited  by  electrolysis  a 
triple  or  quadruple  coating  of  pure  silver.  The  process 
is  similar  to  copper  plating,  the  silver  bath  consisting  of 
potassium  silver  cyanide,  KAg(CN)2.  The  coating  has  a 
frosted  appearance  and  needs  burnishing  or  smoothing 
before  use.  Since  the  coat  deposited  in  this  manner  is 
pure  silver,  these  articles  do  not  stand  as  much  careless 
and  rough  handling  as  the  harder  sterling  or  coin  ware, 
and  much  of  the  coating  is  rubbed  off  in  the  process  of 
cleansing  with  the  so-called  silver  polishes.  Plated  ware 
will  last  much  longer  if  simply  washed  with  hot  water 
and  neutral  soap.  In  order  to  remove  the  tarnish  due  to 
sulphides  (eggs),  soak  the  articles  in  a  clean  tin  or 
aluminium  pan  containing  enough  baking  soda  solution 
to  cover  and  let  them  remain  until  bright.  The  soda 
solution  is  made  by  dissolving  a  tablespoonful  of 
NaHCO3  in  a  quart  of  tepid  water.  Or  the  water  may 
be  made  to  boil  over  the  silver  and  the  soda  added. 

Tin,  (Stannum)  Sn,  occurs  in  Cornwall  and  the  East 
Indies  as  Cassiterite  (tin  stone),  SnO2.  The  ore  is 
crushed  and  washed  to  remove  rock,  roasted  to  oxidize 
sulphide  of  iron  and  copper  and  to  remove  arsenic,  then 


58  HOUSEHOLD   CHEMISTRY 

leached  with  water  to  dissolve  sulphate  of  iron  and  cop- 
per, dried  and  reduced  with  coal  in  a  reverberatory  fur- 
nace. 

Properties. — Tin  is  a  soft,  silver-white,  crystalline 
metal,  malleable  but  not  tenacious.  It  melts  at  about 
230°.  Its  specific  gravity  is  7.3.  On  bending  bar  tin  a 
peculiar  crackling  sound,  called  the  "cry  of  tin,"  is 
heard,  caused  by  the  friction  of  interlaced  crystals. 
Pure  tin  resists  oxidation  in  moist  air,  and  is  not  quickly 
susceptible  to  the  action  of  dilute  acids  and  alkalies. 
However,  there  are  certain  fruits  and  vegetables  which 
attack  the  coating  of  a  tin  can  to  some  extent,  forming 
salts  of  tin  which  are  objectionable.  A  lacquered  can  is 
preferable  for  raspberries,  cherries,  plums,  beets,  pump- 
kin, hominy,  etc.  On  the  other  hand,  cases  of  poisoning 
traced  to  canned  foodstuffs  may  have  been  caused  either 
by  the  imperfect  condition  of  the  food  when  canned  or 
by  careless  soldering.  The  latter  evil  is  now  largely  done 
away  with  by  present  methods  of  sealing  tin  cans. 

Tin  plate  is  made  by  dipping  carefully  cleaned  sheets 
of  iron  or  steel  in  molten  tin.  It  is  much  used  for  roof- 
ing, household  ware  and  cans  for  preserving  food.  Care 
must  always  be  exercised  that  tin  vessels  are  not  over- 
heated, since  the  element  has  a  low  fusion  point  and  will 
run  off  leaving  the  iron  bare,  therefore  it  should  never 
be  used  in  the  oven  or  for  broiling,  roasting  or  frying. 
Liquid  mixtures  may  be  cooked  in  tin  vessels  without 
doing  any  damage. 

Various   useful  alloys  are  known,  viz.,  bronze,   soft 


HOUSEHOLD    CHEMISTRY  59 

solder  (half  tin,  half  lead),  plate  pewter,  antimony,  bis- 

buth  and  copper;  Britannia  metal,  10  per  cent,  antimony. 

EXPERIMENTS. 

1.  Heat  a  small  piece  of  tin  plate  over  the  Bunsen  flame,  note 
the  crystalline  appearance  on  cooling;  treat  a  piece  with  mod- 
erately strong  acid  and  note  a  similar  effect.     Where  have  you 
frequently  seen  this  phenomenon? 

2.  Subject  pieces  of  bright  and  tarnished  tin  to  the  action  of 
dilute  acids  and  alkali  as  under  iron.    Test  the  filtered  liquids 
for  soluble  tin  compounds  by  acidifying  with  HC1  and  adding 
mercuric  chloride.    A   white  precipitate  of  mercurous   chloride 
resuks,   passing  to  a  gray   precipitate  of   metallic   mercury,   if 
sufficient  stannous  chloride  is  present,  the  tin  acting  as  a  reduc- 
ing agent  as  follows : 

SnCl2  +  2HgCl2  ~-»  SnCl4  f  2HgCl, 
aHgCl  -f  SnClj  .-»  SnCl4  +  Hg2. 

Write  the  reactions  for  the  action  of  HC1,  CH3COOH  and 
NaOH  on  tin.  (NaOH  produces  sodium  metastannate  as  the 
final  product.) 

Lead,  Pb  (Plumbum),  occurs  principally  as  galena, 
PbS  (frequently  carrying  silver).  The  metal  is  obtained 
by  roasting  the  ore  until  partially  converted  into  oxide 
and  sulphate.  On  closing  the  furnace  doors  and  increas- 
ing the  heat,  the  charge  is  reduced  to  metal : 

PbS  +  2PbO  — *  3Pb  -|-  SO2. 
PbS  +PbSO4  — -  2Pb  -f  2SOa. 

Lead  is  gray  in  color,  soft,  of  slight  tensile  strength  but 
very  malleable.  Melting-point  325°-335°  and  specific 
gravity  about  1 1.3.  It  is  only  slightly  soluble  in  acids  and 
alkalies,  but  its  oxide  is  very  soluble.  Lead  pipes  are 
formed  by  forcing  warm  lead  through  steel  dies  by 
hydraulic  pressure.  They  are  largely  used  for  conduct- 
5 


6O  HOUSEHOLD   CHEMISTRY 

ing  water  in  the  household.  The  danger  of  drinking 
water  conducted  by  lead  pipes  is  much  exaggerated. 
Unless  the  water  is  unusually  soft,  the  interior  of  the 
pipe  quickly  becomes  coated  with  insoluble  sulphate  and 
carbonate.  A  wise  precaution  with  new  plumbing  is  to 
allow  the  water  to  run  for  some  minutes  before  use. 
Lead  enters  into  many  useful  alloys  previously  men- 
tioned. 

Lead  oxidizes  superficially,  the  compound  formed 
being  the  black  suboxide,  Pb2O,  formerly  used  in  place 
of  graphite  for  lead  pencils. 

The  crystalline  character  of  lead  and  some  of  its  com- 
pounds can  be  shown  by  the  following : 

EXPERIMENTS. 

1.  Dissolve  two  small  portions  of  lead  oxide,  one  in  dilute 
HNOs  and  the  other  in  acetic  acid;  pour  a  little  of  each  solution 
in  two  separate  watch-glasses  and  set  them  aside  to  evaporate. 
Examine  the  crystalline  residue  in  each  case.    Scrape  two  pieces 
of  lead  bright  and  immerse  one  in  strong  nitric  acid,  the  other 
in  acetic  acid ;  allow  them  to  stand  several  days,  then  examine, 
and  compare  with  the  crystals  found  above. 

2.  Immerse  bright  lead  in  water  charged  with  carbon  dioxide ; 
after  several  hours  standing  pour  off  the  water  and  test  it  with 
hydrogen  sulphide. 

3.  Treat  small  pieces  of  bright  and  tarnished  lead  separately 
in  weak  solutions  of  acids  and  alkali  as  under  iron.     Pour  off 
the  clear  solutions,  acidify  with   HNO3  where  necessary,   and 
teat  for  lead  by  passing  H2S  through  the  liquid.    A  black  pre- 
cipitate (PbS)  indicates  lead. 

Summary. — Each  student  should  make  a  tabular  state- 
ment comparing  the  metals  of  the  household  with  regard 
to  action  with  acids  and  alkalies,  cost,  durability,  sus- 


HOUSEHOLD   CHEMISTRY 


6l 


ceptibility  to  oxidation,  methods  of  cleaning,  heat  prop- 
erties, etc. 

USEFUL  TABLES. 


Heat  conductivity 

Specific  heat 

Silver  

IOO.O 

73-o 
48.0 
23.0 
19.0 
15-0 
14.0 
11.9 
u.  6 
8.4 
0.24 

O.2 

0.16 

O.OOI 

0.056 
0.094 
0.218 
0.086 
0.093 

0.055 
0.109 
0.115 
0.117 
0.032 
O.2 
O.2 
0.2 
0.194 

Zinc  

Tin  

Nickel  

Steel  

r&i«M 

CHAPTER  V. 


GLASS,  POTTERY,  AND  PORCELAIN. 

These  materials  belong  to  a  series  of  infusible  and 
insoluble  silicates  of  great  utility  in  all  household  opera- 
tions. Glass  consists  of  a  mixture  of  silicates  in  the 
amorphous  state  and  is  highly  prized  on  account  of  its 
brilliancy  and  transparency;  the  mass  may  be  colored 
without  affecting  either  of  these  qualities.  The  usual 
varieties  of  glass  consist  of  a  mixture  of  alkaline  (with 
alkaline  earth)  or  heavy  metal  silicates,  and  are  known 
as  Bohemian,  Crown,  Bottle  and  Flint  glasses. 

Bohemian  glass  is  a  silicate  of  potash  and  lime.  It  is 
very  infusible  and  insoluble,  therefore  especially  adapted 
for  chemical  purposes. 

Window  or  Crown  glass  is  a  silicate  of  soda  and  lime. 
It  is  more  fusible  but  harder  than  the  Bohemian  and  is 
more  easily  affected  by  acids. 

Bottle  glass  is  an  impure  variety  of  the  above,  colored 
with  iron. 

Flint  glass  is  a  potash  lead  silicate.  This  is  the  most 
fusible  kind  of  glass  and  is  easily  attacked  by  chemical 
reagents;  on  account  of  its  high  refractive  power,  it  is 
much  used  for  optical  purposes. 

All  kinds  of  glass  are  prepared  by  fusing  more  or  less 
pure  silica  in  the  form  of  sand  or  powdered  quartz  with 
the  potash  or  soda  and  lime  or  red  lead,  for  many  hours 
in  large  earthenware  pots,  heated  in  appropriate  fur- 
naces. When  the  mass  has  cleared,  it  is  cast  or  blown 
and  cooled  rapidly  in  order  to  retain  its  transparency. 


HOUSEHOLD   CHEMISTRY  63 

Annealing  is  a  process  of  heating  to  a  temperature 
short  of  softening  and  cooling  slowly,  thereby  reducing 
the  brittleness. 

While  transparency  is  a  very  important  property  of  all 
glasses,  there  are  several  useful  opaque  forms.  Opaque 
glass  is  the  result  of  suspending  finely  divided  infusible 
material  in  the  molten  mass.  Such  materials  are  bone 
phosphates,  cryolite,  zinc  or  tin  oxides,  etc.  The  enamels 
used  on  cooking  utensils  are  of  similar  composition,  and 
should  be  handled  with  the  same  care  as  glass  articles. 
On  account  of  the  great  difference  in  the  expansion  co- 
efficients of  the  glaze  and  metal  base,  too  sudden  cooling 
or  heating  of  the  utensil  should  be  avoided.  Likewise 
judgment  and  care  should  be  exercised  in  the  selection 
and  use  of  cleansing  agents.  Pure  neutral  soap  is  the 
best  medium  to  employ,  and  under  no  circumstances  is 
the  use  of  strong  caustic  alkalies  or  sharp  abrasives 
justified. 

One  of  the  most  characteristic  properties  of  all  glasses 
is  the  solvent  effect  of  hydrofluoric  acid  and  soluble 
fluorides.  Etching  on  glass  is  largely  accomplished  by 
this  means. 

Colored  glass  is  the  result  of  dissolving  some  appro- 
priate mineral  oxide  in  either  variety  of  glass : 

Ruby — oxide  of  gold  or  copper. 

Topaz — sulphide  of   antimony. 

Yellow — silver  chloride  or  borate. 

Green — oxide  of  chromium. 

Blue — oxide  of  cobalt. 

Amethyst — oxide  of  manganese. 


64  HOUSEHOLD   CHEMISTRY 

EXPERIMENTS. 

1.  Corrosive  Action  of  Alkalies — Half  fill  common  prescription 
bottles  (4  oz.)  with  strong  caustic  soda  solution.     Place  them  in 
warm  salt  water,  bring  slowly  to  a  boil  and  continue  for  at 
least  I  hour,  then  cool  slowly,  pour  out  the  contents,  rinse  with 
clean  water  and  examine  the  inner  surface. 

2.  Etching  Tests — (a)  With  a  clean  steel  pen  and  dilute  hy- 
drofluoric acid,  HF,  write  your  name  and  the  date  on  a  clean 
microscope  slide. 

(&)  Thinly  cover  a  clean  watch-glass  with  warm  paraffin. 
When  cool  cut  your  name  with  a  pencil  point  through  the  paraf- 
fin and  immediately  invert  over  a  lead  dish  containing  a  mixture 
of  fluorspar  and  concentrated  sulphuric  acid.  After  half  an 
hour's  gentle  heating,  rub  off  the  paraffin  and  examine  the 
result. 

3.  Detection  of  Arsenic,  Lead,  Etc — Fuse  finely  ground  chips 
of  kitchen  utensil  enamel  with  an  excess  of  potassium  sodium 
carbonate  in  an  iron  or  nickel  crucible,  cool  and  extract  the 
melt  with  hot  water.    Filter  and  wash  the  residue  several  times 
with  hot  water.     Test  the  filtrate  for  arsenic,  lead,  and  acids, 
by  dividing  it  into  3  parts — two  of  one-quarter  each  and  the  third 
the  remaining  half. 

Part  I.  Test  for  arsenic  by  making  strongly  acid  with  HC1 
and  boiling  with  a  strip  of  clean  copper.  A  gray  or  black  coat- 
ing indicates  arsenic. 

Part  II.  Make  acid  with  HC1  and  pass  H2S  rapidly  through 
the  solution.  A  black  precipitate  indicates  lead. 

Part  III.  One-half  of  the  solution — tests  for  sulphates,  borates, 
phosphates,  and  silicates,  as  follows : 

Neutralize  with  HC1,  if  any  precipitate  forms,  filter  and  divide 
the  filtrate  into  3  parts.  The  residue  is  silicates.  Take  I  part 
of  the  filtrate,  thoroughly  moisten  a  strip  of  turmeric  paper  with 
it  and  dry  at  100  °  C.  A  pink  color  indicates  borates. 

To  another  part,  add  barium  chloride  and  a  few  drops  of  HC1. 
A  white  crystalline  precipitate  indicates  sulphates.  Pour  a  few 


HOUSEHOLD   CHEMISTRY  65 

drops  of  the  remaining  part  into  an  excess  of  ammonium  molyb- 
date.  Warm  gently  and  a  yellow  color  or  yellow  crystalline 
precipitate  indicates  phosphate. 

Porcelain  and  Pottery  are  fused  silicates  of  alumina, 
the  former  pure,  and  the  latter  contaminated  with  oxides 
of  iron,  manganese,  etc. 

The  primary  source  of  these  wares  is  clay,  a  highly 
infusible  hydrated  silicate  of  alumina.  For  porcelain 
making  it  is  mixed  with  some  fusible  silicate  such  as 
feldspar,  and  a  small  quantity  of  water,  moulded  into 
shape,  dried  and  heated  in  a  furnace  for  many  hours. 
The  feldspar  or  flux  only  melts  and  running  through  the 
porous  mass  cements  it  together.  Even  after  firing,  the 
ware  requires  coating  with  the  glaze,  a  mixture  of  slight- 
ly fusible  material  suspended  in  water  into  which  the  ar- 
ticle is  dipped.  It  is  dried  and  returned  to  the  furnace 
for  heating.  The  glaze  is,  in  effect,  a  true  glass  and 
makes  the  mass  impenetrable  to  liquids.  Decorative 
effects  are  produced  in  two  ways,  called  under-  and  over- 
glaze,  of  which  the  former  is  the  better  and  more  per- 
manent. For  under-glaze  work,  finely  ground  colored 
glass  suspended  in  turpentine  is  applied  to  the  unglazed 
ware  and  afterwards  "fired"  at  the  high  temperature  of 
the  porcelain  furnace.  The  glaze  is  subsequently  applied 
and  fired  as  before.  Over-glaze  decoration  admits  of 
the  use  of  colors  which  may  be  injured  by  the  high  heat 
of  the  porcelain  furnace  and  is  applied  at  a  lower  tem- 
perature in  a  muffle.  The  colors  consist  of  various 
oxides  mixed  with  borax,  litharge,  nitre,  etc.  They  are 
applied  in  watery  solution. 


66  .          HOUSEHOLD   CHEMISTRY 

Stoneware  is  an  impure  form  of  porcelain,  somewhat 
more  fusible  and  usually  glazed  with  borax.  The  finer 
qualities  are  known  as  china.  Earthenware  and  brick 
consist  of  clay  and  sand,  mixed  with  water,  moulded, 
dried  and  fired  in  a  kiln.  The  former  is  usually  glazed 
with  salt,  while  the  latter  is  left  in  the  porous  state. 

Since  most  of  our  decorated  table  china  is  over-glaze 
ware  it  is  likely  that  it  will  not  successfully  withstand 
repeated  washings,  especially  since  modern  practice  has 
brought  into  use  many  forms  of  alkaline  detergents,  i.  e., 
soap  powders  and  cleaners.  Some  of  these  contain 
bleaching  agents,  which  liberate  chlorine  and  are  there- 
fore destructive  to  gold,  but  prolonged  contact  with  the 
strong  alkalies  in  their  composition  is  sufficient  to  hasten 
the  removal  of  both  gold  and  color  decoration. 

EXPERIMENTS. 

1.  Heat  several  decorated  dishes  in  new  enameled  saucepans 
with  solutions  of  various  soaps  and  other  cleansers.     Keep  the 
pans  covered  and  boil  gently  for  I  hour.     Cool,  rinse  in  clear 
water,  and  examine  the  effect,  both  on  the  china  and  the  sauce- 
pan. 

2.  Porosity — Weigh   small   pieces   of   dry   unglazed   porcelain 
and  earthenware,  soak  over  night  in  water,  wipe  dry  and  weigh 
again.    Calculate  the  per  cent,  of  water  absorbed. 

3.  Fusibility — Heat  small  splinters  of  porcelain  and  earthen- 
ware held  in  platinum  wire  (spiral)  at  the  highest  heat  of  your 
burner.    Cool  and   examine  with  a  magnifier.    Are   the  edges 
sharp  or  rounded? 

4.  Testing  for  Lead  in  the  Glaze — Boil  the  article  for  some 
time  in  caustic  soda,  cool  the  liquid  and  add  (NH«)2S.    A  dark- 
ening of  the  liquid  or  a  black  precipitate  due  to  lead  sulphide, 
PbS,  indicates  lead. 


CHAPTER  VI. 


FUELS. 

Fuels  are  materials  used  for  producing  heat;  they 
must  be  capable  of  uniting  with  oxygen  under  easily 
obtainable  conditions  and  of  evolving  much  heat  energy 
during  the  process  of  combustion.  Occurring  as  gases, 
liquids  and  solids,  carbon  and  its  compounds  largely  fill 
the  required  conditions. 

Classification. — A  logical  arrangement  of  the  fuels 
would  result  as  follows: 

Hydrogen 

Hydrocarbons 

Carbon 

monoxide 
Hydrocarbons 
Hydrocarbons 
Alcohols 
Hydrocarbons 
Anthracite 


f  Natural 


Pure  fuels 


Gases 


Liquids 


I  Artificial 


Impure  fuels 


Solids 


Solids 


Natural 
Artificial 
Natural 
Artificial 


r  Coke 
\  Charcoal 

[  Soft  coal 
\ 


Natural  -j    Peat 

L  Woods 

Coals,  petroleum  and  natural  gas  are  evidently  of  plant 
and  animal  origin,  produced  by  a  natural  method  of 
decomposition,  similar  to  a  process  of  dry  distillation. 

The  terms  pure  and  impure  are  used  in  a  restricted 
sense,  the  former  signifying  that  the  substance  is  ready 
for  direct  combustion,  while  in  the  latter  case  a  number 
of  complicated  chemical  changes  must  take  place  before 


68  HOUSEHOLD   CHEMISTRY 

combustion  is  possible.  This  is  explained  in  detail  in 
the  discussion  of  the  composition  of  wood. 

Historical:  Woods  both  hard  and  soft  and  charcoal 
have  been  used  from  the  earliest  times.  Peat,  a  form  of 
partly  carbonized  turf,  was  the  main  fuel  of  European 
countries  during  the  Middle  Ages  and  is  still  in  use. 
Soft  coal  came  into  use  during  the  I5th  century,  while 
gas  and  hard  coal  were  first  employed  in  the  early  part 
of  the  i Qth  century,  and  hydrocarbons  about  the  middle 
of  the  same  epoch.  Alcohol  is  just  coming  into  gen- 
eral use  in  our  own  times. 

Impure  solid  fuels  on  account  of  more  extended  use 
will  be  first  discussed. 

Wood,  peat  and  soft  coal  are  such  impure  forms  of 
fuel  and  must  undergo  so  many  and  such  complicated 
chemical  changes  before  they  are  capable  of  yielding 
heat,  that  their  actual  fuel  value  is  frequently  over-esti- 
mated and  rarely  understood  by  the  consumer.  The  fol- 
lowing is  a  brief  and  simple  statement  of  composition 
and  changes  to  be  expected: 

Wood  contains,  moisture,  (H2O)  ;  resin,  (CXHX)  ; 
starch,  gum,  and  cellulose,  «(C,H]0O6);  oil,  (C^H^CX); 
mineral  matter  or  ash. 

Considerable  heat  is  required  to  drive  off  the  mois- 
ture and  raise  the  starch,  cellulose,  etc.,  to  such  tempera- 
tures that  they  will  decompose,  yielding  gases  of  a  com- 
bustible nature,  for  example  CO,  CH4,  C2H4,  C2H2,H2; 
in  this  decomposition  H2O  is  formed  and  must  be  driven 
off  as  a  gas.  Much  heat  is  also  absorbed  by  the  ash  in 
forming  new  chemical  compounds.  In  fact  the  fuel  effi- 


HOUSEHOLD    CHEMISTRY  69 

ciency  of  wood  depends  entirely  upon  the  relative  vol- 
umes of  combustible  gas  and  charcoal  furnished,  and 
as  the  charcoal  or  carbon  is  the  best  solid  fuel,  the  wood 
furnishing  the  largest  proportion  of  carbon  in  this  form 
is  the  best  fuel,  hence  we  find  it  advantageous  to  use 
hardwood.  It  must  be  understood  that  carbon  or  char- 
coal at  a  red  heat  combines  with  a  limited  amount  of 
oxygen  and  forms  a  combustible  gas,  carbon  monoxide, 
CO,  a  fuel  of  the  highest  heating  efficiency. 

Soft  coal,  a  partly  carbonized  plant  product,  produces 
less  water  by  chemical  change  and  yields  the  combustible 
gases  and  carbon  (coke)  in  larger  proportion. 

Hard  coal  is  superior  to  soft,  since  it  is  a  purer  form 
of  carbon  and  yields  very  little  combustible  gas. 

EXPERIMENT. 

To  determine  the  value  of  coal  or  wood  for  fuel  purposes, 
proceed  as  follows :  Take  i  gram  of  pulverized  coal  or  small 
pieces  of  wood  in  a  weighed  crucible,  dry  at  120°  with  cover 
off,  cool  and  weigh;  the  loss  is  water.  Heat  the  crucible  with 
cover  on  in  a  strong  Bunsen  flame  for  7  minutes,  cool  and  weigh ; 
the  loss  is  volatile  combustible  matter  (tar,  smoke,  etc.).  Heat 
again  with  cover  off  until  nothing  remains  but  ash.  This  opera- 
tion will  require  some  time ;  cool  and  weigh ;  the  loss  is  fixed 
carbon  (actual  fuel).  Subtract  the  weight  of  the  crucible;  the 
difference  is  ash. 

The  quantity  of  ash  in  coals  is  always  greater  than  in 
wood,  owing  to  the  presence  of  foreign  mineral  sub- 
stances such  as  silica,  lime  and  sulphide  of  iron  derived 
from  the  earthy  strata  in  which  the  coal  is  deposited. 

Flue  dust,  collecting  in  stove  pipes  and  flues  where 
hard  coal  is  burned,  contains  sulphate  of  ammonia. 


7O  HOUSEHOLD   CHEMISTRY 

When  cool,  this  salt  absorbs  water  and  attacks  iron, 
rapidly  corroding  the  pipes.  This  fact  explains  the  neces- 
sity of  cleaning  the  smoke  pipes  of  furnaces  and  stoves 
in  the  spring  of  the  year  when  the  heating  apparatus  is 
no  longer  used. 

EXPERIMENT. 

Collect  some  of  the  light  gray  dust  from  a  smoke  pipe,  treat 
about  I  gram  with  boiling  water  on  a  filter,  pouring  the  liquid 
through  several  times.  Reserve  the  residue  and  test  the  liquid  in 
the  usual  manner  for  ammonia  and  sulphates.  Extract  the 
residue  still  on  the  filter-paper  with  boiling  dilute  HC1  until 
the  residue  is  light  in  color.  This  is  mainly  silica  from  the 
coal  ash.  Test  the  acid  filtrate  for  ferric  iron  and  lime  in  the 
usual  manner. 

Liquid  Fuels. — These  comprise  alcohols,  and  hydro- 
carbons in  the  form  of  gasoline  or  naphtha,  and  kero- 
sene. The  hydrocarbons  are  highly  inflammable  liquids 
obtained  from  crude  petroleum. 

The  distillation  of  petroleum  was  carried  on  in  Europe 
early  in  the  i8th  century,  and  there  is  evidence  of  the 
use  of  the  crude  oil  by  fire  worshippers  as  far  back  as 
Zoroaster.  The  great  oil  region  of  Europe  is  the  Baku 
peninsula  on  the  Caspian  Sea.  Crude  petroleum  was 
known  to  the  Indians  in  America,  and  in  New  York 
State  it  became  popular  as  a  specific  for  rheumatism, 
under  the  name  of  Seneca  Oil.  Refined  petroleum  in 
the  United  States  dates  from  1855,  when  it  was  distilled 
and  put  on  the  market  as  a  patent  medicine  called  Amer- 
ican Oil.  Up  to  this  time  a  limited  quantity  had  been 
obtained  at  or  near  the  surface  of  the  ground.  In  1859, 
in  Titusville,  Pa.,  Col.  Drake  applied  the  method  of 


HOUSEHOLD   CHEMISTRY  71 

boring  artesian  wells  to  obtain  petroleum  from  under- 
lying strata,  and  the  industry  was  revolutionized.  In 
that  year  2,000  barrels  of  crude  petroleum  were  produced, 
2  years  later  2,000,000,  and  in  1910  210,000,000  barrels. 
The  new  supply  gave  a  material  more  profitable  for  refin- 
ing than  shale  oil.  By  fractional  distillation  at  first,  a 
number  of  distillates  were  obtained  ranging  from  petro- 
leum ether,  naphthas,  gasoline,  etc.,  to  solid  paraffins.  The 
yield  of  gasoline  by  this  process  was  entirely  insufficient, 
however,  to  meet  the  sudden  demand  created  by  the  auto- 
mobile and  motor  engines,  so  a  system  of  "cracking"  was 
devised,  which  has  greatly  increased  the  light  oil  dis- 
tillate, and  is  better  suited  to  the  refining  of  oils  from 
the  newer  western  fields. 

Cracking  Process. — This  is  a  method  of  distilling  at  a 
temperature  higher  than  the  normal  boiling  points  of 
the  constituents  to  be  obtained,  which  effects  a  dissocia- 
tion of  many  of  the  heavier  oils  into  lighter  hydrocar- 
bons. As  the  process  is  conducted  in  some  places,  the 
charge  of  oil  (about  1,000  barrels)  is  put  into  a  side- 
firing  still,  the  temperature  is  raised  to  600°  or  700°  F., 
and  the  vapors  as  they  come  off  are  carried  to  a  series 
of  condensers,  where  they  are  separated,  the  heaviest 
vapors  condensing  first,  the  lightest  traveling  farthest 
before  being  condensed.  The  vapors  of  a  considerable 
amount  of  the  oil  intermediate  between  kerosene  and 
lubricating  oils  are  returned  to  the  still,  superheated,  and 
decomposed,  so  increasing  the  yield  of  light  distillate. 
Usually  3  streams  of  oil  of  different  specific  gravities 


72  HOUSEHOLD   CHEMISTRY 

are  simultaneously  received :  the  heaviest,  or  the  paraffin 
oil  distillate;  the  intermediate,  or  gas  oil,  and  the  light 
oil  distillate.  The  paraffin  oil  distillate  is  worked  up 
to  produce  lubricating  oils,  paraffin,  etc.,  the  intermed- 
iate distillate  is  refined  for  burning  and  gas  oils,  and  the 
light  distillate  is  fractionally  distilled  and  yields  a  num- 
ber of  important  compounds,  such  as : 

Cymogene,  specific  gravity  110°  Baume.  Used  in  the 
manufacture  of  ice. 

Rhigolene,  specific  gravity  100°  Baume.  Used  as  an 
anaesthetic. 

Petroleum  ether,  85°-8o°  Baume.  Used  as  a  solvent 
and  for  carbureting  air  in  gas  machines. 

Benzine,  89°-82°  Baume.    A  solvent. 

Gasoline.  Varies  widely  in  specific  gravity  and  qual- 
ity, according  to  the  demand.  It  may  have  a  specific 
gravity  of  8o°-6o°  Baume. 

For  the  purification  of  petroleum  products  the  use  of 
sulphuric  acid  followed  by  soda  lye  is  universal.  Aro- 
matic hydrocarbons,  fatty  and  other  acids,  phenols  and 
tarry  bodies  are  thus  decomposed  or  removed.  Sulphur 
compounds  are  taken  out  in  the  form  of  sulphides  by 
copper. 

Chemical  Nature  of  Petroleums. — Crude  petroleum  from 
different  fields  shows  great  differences  in  chemical  con- 
stituents. The  Pennsylvania  petroleum  yields  hydro- 
carbons of  the  methane  series  principally,  compounds 
from  C4H10  to  C35H72  having  been  isolated  in  almost  un- 
broken sequence,  with  many  of  their  isomeric  forms. 


HOUSEHOLD   CHEMISTRY  73 

Ring  hydrocarbons  such  as  benzene,  C6H6,  have  also 
been  found  in  smaller  quantity. 

The  California  oils  are  of  varied  character  and  con- 
sist of  a  more  or  less  dense  asphaltic  base.  Asphalt  is 
usually  regarded  as  evaporated  and  oxidized  petroleum. 
Phenols  are  common  constituents;  nitrogenous  ring 
compounds  and  the  olefines  from  C2H4  to  C30H30  in- 
clusive have  been  obtained.  The  California  field  is  very 
active,  a  single  well  having  made  a  record  of  30,000  to 
60,000  barrels  per  day. 

The  Texas  oil  seems  to  combine  the  characteristics  of 
the  Pennsylvania  and  the  California  types,  while  the  mid- 
western  field  produces  both  kinds. 

Russian  and  Cuban  petroleum  consist  largely  of  the 
unsaturated  hydrocarbons  of  the  naphthene  series, 

CnH2n  — 6  H~    H6. 

The  depth  at  which  petroleum  is  found  is  of  interest. 
In  Pennsylvania  wells  range  from  300  to  3,700  feet;  in 
California  they  have  been  drilled  to  a  depth  of  over 
4,000  feet. 

Products  of  Combustion. — At  temperatures  slightly 
above  normal  liquid  fuels  readily  combine  with  oxygen, 
producing  intense  heat  and  yielding  water  and  carbon 
dioxide  as  products  but  no  ash;  with  too  small  supply 
of  oxygen  the  temperature  of  combustion  is  much  low- 
ered and  a  large  part  of  the  carbon  is  not  consumed  and 
escapes  in  a  free  state,  producing  a  yellow  flame  and  if 
in  great  excess  much  black  smoke — a  very  familiar  phe- 
nomenon in  kerosene  lamps. 


74  HOUSEHOLD   CHEMISTRY 

With  great  excess  of  oxygen,  as  when  the  hot  vapor 
of  these  liquids  is  mixed  with  many  times  its  volume 
of  air,  in  a  confined  space,  the  combustion  is  so 
rapid  as  to  produce  an  explosion  (automobile  engine). 
When  using  these  products  for  fuel  purposes  care  must 
be  taken  that  these  last  conditions  do  not  exist.  Hence 
as  a  measure  of  safety  the  lamp  or  stove  reservoir  is 
kept  well  filled  and  cool.  The  following  simple  experi- 
ments will  serve  to  impress  these  important  facts  on  the 
student's  mind: — 

EXPERIMENTS. 

1.  Pour  not  more  than  i  or  2  drops  of  clean  gasoline  into  a 
clean,  dry,  wide-mouth  bottle  of  12  to  16  ounces  capacity,  stir 
the  vapor  for  a  moment  with  a  hot  glass  or  iron  rod  and  bring 
a  lighted  match  over  the  mouth  of  the  bottle;  a  slight  but  per- 
ceptible explosion  should  result  with  or  without  blue  flame. 

2.  Pour  a  teaspoonful  of  the  same  liquid  in  a  shallow  porcelain 
dish   or  saucer,   apply  the  lighted  match  and   note  the  yellow 
flame,  but  no  explosion.    Quench  by  covering  with  cloth,   stiff 
cardboard  or  any  article  that  will  exclude  air. 

Gasoline  is  used  quite  largely  in  some  localities  as  a 
source  of  heat,  being  consumed  in  the  so-called  blue 
flame  stove,  which  operates  by  heating  the  liquid  to  such 
a  temperature,  air  being  excluded,  that  vapor  forms  rap- 
idly and  under  slight  pressure.  It  is  then  conducted  to 
the  burner  (Bunsen),  mixed  with  the  proper  amount  of 
air,  and  burns  with  a  blue  flame.  These  stoves  and 
heaters  are  perfectly  safe  as  long  as  they  are  kept  clean, 
do  not  leak  liquid,  are  kept  well  filled  and  furnished 
with  good  gasoline.  The  quality  of  gasoline  may  be 
determined  by  the  following  tests : 


HOUSEHOLD   CHEMISTRY  75 

1.  Observe  the  color,  it  should  be  white  as  water. 

2.  Clearness;  if  cloudy,  dirt  or  water  is  present.    Evaporate 
a  small  quantity  in  a  clean  porcelain  dish  over  warm  water  (no 
flame)  and  examine  the  residue;  also  filter  some  through  clean 
dry  chamois  skin.    Water  and  dirt  will  remain  on  the  skin.     It 
is  a  wise  precaution  for  users  of  gasoline  for  any  purpose  to 
filter  as  above  before  using. 

3.  Test  with  delicate  litmus  paper;  it  should  be  neutral. 

4.  Determine  the  specific  gravity  with  the  Baume  hydrometer 
for  light  liquids;  it  should  register  not  higher  than  72°  for  fuel 
purposes. 

Kerosene,  erroneously  called  an  oil,  is  much  more 
extensively  used  and  widely  known;  it  is  probably  the 
cheapest  and  best  liquid  illuminating  agent  of  the  present 
day.  The  ordinary  kerosene  wick  lamp  is  so  well  known 
as  to  need  no  explanation.  Kerosene,  however,  is  used 
in  blue  flame  stoves,  such  as  the  Khotal,  etc.,  and  al- 
though more  troublesome  to  manipulate  is  preferred  by 
most  people  because  the  danger  is  minimized. 

Kerosene  should  successfully  stand  tests  i,  2,  3,  given 
under  gasoline.  The  specific  gravity  should  be  48° 
Baume. 

In  addition,  flash  and  fire  tests  are  prescribed  in  most 
parts  of  the  world.  The  former  signifies  the  temper- 
ature at  which  the  oil  gives  off  ignitable  vapor,  and  the 
latter  the  point  at  which  it  takes  fire.  The  experiment 
below  represents  the  open-cup  method  of  determining 
the  flash  point,  the  figures  of  which  are  always  slightly 
lower  than  by  other  methods : 

Half   fill   a  200  cc.  beaker  with  kerosene,   place  over  warm 
water,  stir  gently  with  an  accurate  Fahrenheit  thermometer  and 
heat  slowly  not  more  than  2°  rise  per  minute,  until  a  small  open 
6 


76  HOUSEHOLD   CHEMISTRY 

flame  brought  over  the  surface  of  the  oil  causes  a  blue  flame 
and  slight  explosion.  Note  the  temperature,  it  is  the  flash  point 
and  should  not  be  lower  than  100°  F.  Air  currents  and  draughts 
should  be  excluded  in  this  experiment. 

Kerosene  and  gasoline  are  unsaponifiable.  Prove  this 
in  the  case  of  kerosene  by  the  following: 

Heat  a  small  quantity  of  kerosene  with  one-seventh  its  volume 
of  a  solution  of  sodium  hydroxide  (38°  Baume)  over  hot  water, 
stirring  often.  On  cooling,  does  the  product  resemble  soap? 
Is  kerosene  rightly  called  an  oil? 

The  increased  efficiency  of  kerosene  as  a  burning  fluid 
in  recent  years  is  partly  due  to  the  presence  in  its  com- 
position of  unsaturated  hydrocarbons,  formed  during 
the  cracking  process.  These  have  a  higher  illuminating 
power  than  the  former  saturated  type  found  in  the  oil. 

Alcohols. — Of  this  series,  only  methyl  or  wood  alcohol 
and  ethyl  or  grain  alcohol  are  used  as  fuels.  A  mixture 
of  the  two  (90  parts  ethyl,  9  parts  methyl  -f-  I  part  ben- 
zine) has  come  into  general  use  under  the  name  of  de- 
natured alcohol ;  it  is  essentially  ethyl  alcohol.  Methyl 
alcohol,  CH3OH,  is  produced  commercially  by  the  dry  dis- 
tillation of  wood  and  is  known  as  pyroligneous  or  wood 
spirit ;  it  contains  light  wood  tar,  acetone,  and  acetic  acid, 
which  should  be  completely  removed  before  using,  leaving 
a  bland  mild-smelling  liquid  similar  to  ethyl  alcohol, 
known  as  Columbian  Spirit.  Much  of  the  ordinary  wood 
alcohol  as  quite  impure.  Tar  and  acetone  are  easily  dis- 
tinguished by  the  color  and  odor,  especially  if  gently 
heated ;  acid  is  readily  shown  by  litmus  paper. 

As  a  burning  fluid  methyl  alcohol  is  distinctly  inferior 


HOUSEHOLD    CHEMISTRY  77 

to  grain  alcohol.  The  following  equation  shows  the 
chemical  change  during  complete  oxidation:  2CH3OH 
+  30,  — •  4H,0  +  2C02. 

In  stoves  or  lamps  of  the  best  type,  ethyl  or  grain 
alcohol  burns  as  follows: 

C,H5OH  +  30,  «~  2C02  +  3H20. 

Comparing  this  equation  with  that  of  methyl  alcohol 
it  will  be  seen  that  the  amount  of  CO2  is  doubled,  hence 
it  is  fair  to  assume  that  the  heating  effect  is  greater; 
ethyl  alcohol  is  less  volatile  than  methyl,  therefore  loss 
by  evaporation  during  use  is  less. 

Methyl  alcohol  is  readily  oxidized  to  formaldehyde  by 

means  of  hot  copper  oxide  (see  Experiment  I,  p.  52). 

This  serves  as  a  test  for  the  identification  of  this  alcohol. 

By  further  oxidation  methyl  alcohol  yields  formic  acid: 

CHSOH  +  Oa  —  HCOOH  +  H,O. 

Ethyl  or  grain  alcohol,  C2H5OH,  is  prepared  by  the 
fermentation  of  glucose  or  maltose  by  means  of  yeasts 
and  distillation  of  the  product.  It  is  a  colorless  liquid 
with  pleasant  and  characteristic  odor,  usually  containing 
about  95  per  cent,  of  pure  alcohol  and  the  balance  water 
and  small  amounts  of  impurities,  acetic  acid  and  acetone 
more  especially;  these  are  not  particularly  objectionable 
if  the  liquid  is  to  be  used  for  generating  heat  or  general 
solvent  purposes,  but  in  many  chemical  operations 
further  purification  is  necessary.  Pure  alcohol,  free 
from  aldehyde  and  acid  for  chemical  purposes,  can  easily 
be  made  from  the  ordinary  95  per  cent,  variety  or  even 
waste  alcohol  by  allowing  it  to  remain  for  several  days 


78  HOUSEHOLD   CHEMISTRY 

in  contact  with  slightly  rancid  tallow  or  grease  and  sub- 
sequently filtering,  distilling  and  neutralizing  the  product. 
On  account  of  the  high  price,  due  to  the  government 
tax,  ethyl  alcohol  was  formerly  little  used  for  heat  and 
power  purposes,  but  since  the  introduction  of  denatured 
alcohol,  the  cost  has  fallen  to  50  cents  per  gallon  and 
the  use  enormously  increased.  At  the  present  price,  it  is 
little  more  expensive  to  use  than  gasoline  and  far  safer 
and  pleasanter  to  handle. 

EXPERIMENTS. 

1.  Determine  the  boiling  point  of  95  per  cent,  ethyl  alcohol  by 
distilling  100  cc.  in  a  small  flask  fitted  with  a  thermometer  and 
condenser. 

2.  Determine  the  specific  gravity  of  alcohol  by  means  of  the 
hydrometer  and  check  the  result  by  the  Westphal  balance. 

3.  Ethyl  alcohol  combines  with  iodine  in  the  presence  of  strong 
alkali,  forming  iodof orm : 

C,H5OH  +  4I2  +  NasCOs  — »  2CHI3  +  CO2  +  2NaI  +  2H2O. 

To  3  cc.  of  CzHsOH  and  an  equal  amount  of  tincture  of  iodine 
in  a  test  tube,  add  NasCOs  in  small  amounts,  shaking  after  each 
addition  and  warming  gently  until  the  solution  is  just  decolorized 
and  yellow  crystals  of  iodof  orm  appear.  About  5  cc.  of  Na2CO3 
will  be  used. 

4.  By  the  use  of  an  oxidizing  agent  such  as  KzCnOr,  ethyl 
alcohol  is  converted  into  acetaldehyde : 

3C,H6OH  +  K2Cr,07  +  4H2SO,  _» 

3CH3CHO  +  K2S04  +  Cr2(S04)s  +  7H,O. 
Heat  10  cc.  of  alcohol  with  i  cc.  of  KaCrzO?  solution  acidified 
with  sulphuric  acid,  notice  the  reduction  of  the  chromium  to 
base  and  the  odor  of  aldehyde. 

5.  Since   ethyl   alcohol  oxidizes   readily  to  acetic  acid,   some 
acidity  is  found  in  most  samples.    The  amount  may  be  such  as 


HOUSEHOLD   CHEMISTRY  79 

to  cause  corrosion  of   metal  containers  or  burners  in  alcohol 
stoves. 

Determine  the  acidity  of  10  cc.  of  alcohol  with  N/io  alkali, 
calculating  the  percentage  in  terms  of  acetic  acid. 

Gases. — Gas  consisting  of  hydrogen,  carbon  monoxide, 
and  various  hydrocarbons  is  the  ideal  fuel.  There  are 
seven  varieties  in  use  for  fuel  and  lighting  purposes,  viz. : 

Natural  gas 
Water  gas 

Coal  gas 
Gases  proper  <  Acetylene  gas 

Blau  gas 
Pintsch  gas 

f  Cold  air  charged  with  naphtha 
Naphtha  or  air  gas  < 

L      vapor. 

Natural  gas  has  been  found  in  large  pockets  in  the 
earth  in  various  localities  for  many  years.  The  shrines 
of  antiquity  were  in  some  cases  supplied  with  gas  from 
crevices  in  the  earth;  it  is  probable  that  the  temple  of 
Diana  at  Ephesus  had  a  natural  gas  well. 

Fredonia,  N.  Y.,  was  lighted  with  natural  gas  as  early 
as  1825.  The  supply  was  accidentally  discovered  when 
boring  for  salt,  as  these  earth  pockets  are  reached  by 
drilling  as  for  oil  or  brine.  The  gas  comes  out  under 
tremendous  pressure,  which  must  be  controlled  and  re- 
duced for  household  use.  Its  main  constituent  is  meth- 
ane or  marsh  gas,  which  has  little  or  no  illuminating 
power,  but  is  an  excellent  source  of  heat.  The  supply 
of  natural  gas  from  earth  pockets  is  gradually  becoming 
exhausted. 

Three  classes  of  natural  gas  are  recognized : 


8O  HOUSEHOLD   CHEMISTRY 

(1)  The  gas  which   issues   from  marshy  beds,   and 
contains  methane  as  its  only  combustible  constituent. 

(2)  Natural  gas   found   in  pockets   occurring  in   oil 
fields  but  not  associated  with  oil.     In  this,  methane  pre- 
dominates, but  hydrocarbons  higher  in  the  series   are 
found.     This  is  the  gas  which  supplies  Pittsburgh  and 
Cleveland. 

(3)  A  Sas  associated  with  petroleum,   called  "wet" 
gas,  from  which  gasoline  can  be  obtained.     Natural  gas 
of  this  type  is  found  in  almost  every  oil-producing  state 
of  the  union.     By  compressing  this  gas  to  350  pounds  per 
square  inch,  and  passing  it  through  cooled  condenser  coils, 
a  gasoline  is  produced  with  specific  gravity  of  77°  to  110° 
Baume.  Being  extremely  volatile,  it  is  kept  in  tanks  under 
heavy  pressure,  and  when  drawn  off  is  usually  mixed 
at  once  with  low  grade  refinery  naphthas.    The  amount 
of  gasoline  obtained  in  the  last  few  years  from  natural 
gas  has  approximated  10,000,000  gallons  annually.    The 
residual  gas  left  after  the  gasoline  extraction  has  a  high 
heating  value  and  is  utilized  for  that  purpose. 

Water  Gas. — By  passing  steam  at  high  pressure  over 
incandescent  carbon  a  mixture  of  hydrogen  and  carbon 
monoxide,  known  as  water  gas,  is  produced.  The  carbon 
used  may  be  in  the  form  of  anthracite,  coke,  or  even 
charcoal.  A  high  temperature  is  necessary  for  the 
operation,  usually  about  3,000°  F.  Decomposition  takes 
place,  the  chemical  change  being  as  follows : 

2H20  +  C,  — >  2CO  +  2H2. 
In  order  to  give  the  resulting  gases  illuminating  quality 


HOUSEHOLD   CHEMISTRY  8 1 

they  are  mixed  with  light  hydrocarbons  and  the  com- 
bination passed  through  a  red  hot  zone.  The  naphtha 
vapors  are  broken  up  (cracked)  into  permanent  gases 
such  as  methane,  ethylene  and  acetylene,  giving  the  prod- 
uct a  composition  similar  to  coal  gas  (q.  v.)  but  com- 
bined in  somewhat  different  proportions.  Since  it  con- 
tains more  carbon  monoxide  it  is  generally  regarded  as  a 
better  fuel. 

Coal  Gas. — From  soft  or  bituminous  coals,  a  gas  can 
be  produced  by  dry  distillation.  This  was  the  first 
method  used  for  making  gas,  and  dates  back  to  early 
days  of  the  iQth  century.  On  account  of  the  many  and 
valuable  by-products  produced,  viz.,  ammonia,  coal  tar, 
carbolic  acid,  naphthalene,  cyanides,  etc.,  it  will  probably 
be  used  for  many  years  to  come. 

The  process  consists  in  heating  the  coal  in  large  clay 
retorts,  drawing  off  and  cooling  the  gas  in  order  to  con- 
dense tar,  washing  to  remove  ammonia,  tar,  etc.,  remov- 
ing sulphur  with  lime  or  iron  oxide,  storing  and  deliver- 
ing the  gas  under  slight  pressure.  Essentially  the  same 
process  of  purification  is  used  with  water  gas.  In  recent 
years  the  horizontal  retort  for  the  distillation  of  the  coal 
has  been  generally  superseded  by  the  inclined  or  vertical 
type.  The  charge  of  coal  is  admitted  at  the  top  and  the 
retort  filled.  When  the  distilling  process  is  complete,  the 
bottom  of  the  retort  is  opened,  and  the  residue,  coke, 
falls  out  by  gravity. 

The  changes  which  take  place  when  soft  coal  is  thus 
burned  out  of  contact  with  air  are  extremely  compli- 


82 


HOUSEHOLD   CHEMISTRY 


cated.  The  products  formed  are  gaseous,  liquid,  and 
solid.  The  liquid  constituents  which  condense  as  coal 
tar  yield  on  further  treatment  a  number  of  substances 
such  as  benzol  and  anthracene,  which  are  the  basis  of 
thousands  of  important  organic  compounds.  The  gas- 
eous products,  which  are  combined  as  illuminating  gas, 
are  conveniently  classified  as  follows: 

Impurities  or  diluents — oxygen,  carbon  dioxide,  nitro- 
gen. 

Illuminants — ethylene,  acetylene. 

Gas  proper — hydrogen,  marsh  gas  or  methane,  car- 
bon monoxide. 

Hydrogen  sulphide  is  the  only  impurity  in  gas  of  any 
importance;  by  its  combustion  sulphur  dioxide  and  water 
are  produced,  finally  resulting  in  sulphurous  acid,  which 
readily  attacks  fabrics  and  metals  and  bleaches  many 
colors.  Any  hydrogen  sulphide  escaping  combustion 
blackens  lead  acetate  paper  held  far  enough  above  the 
flame  to  be  uninfluenced  by  the  heat. 

Analyses  of  gas  are  given  below: 


Water  gas  per  cent. 

Coal  gas 

0.0 

12.6 
0.9 

27-3 
27.7 
27.7 
3-8 

0.0 

6-5 
0.9 
6.8 
41.1 

41.0 
3-7 

100.  0 

25.4 

100.  0 

21.32 

HOUSEHOLD   CHEMISTRY  83 

In  a  water  gas,  the  candle-power  is  usually  double  the 
illuminants. 

The  value  of  gas  is  expressed  as  candle-power,  the 
unit  being  a  standard  sperm  candle  burning  2  grains 
per  minute;  hence  a  25-candle-power  gas  would  give 
as  much  light  as  25  of  the  candles  burning  simultane- 
ously. The  calorific  value  of  the  gas  should  also  be  de- 
termined as  a  measure  of  its  quality  for  general  pur- 
poses. 

The  standard  illuminating  burner  consumes  5  cubic 
feet  per  hour  under  a  pressure  of  il/2  inches  of  water. 
This  is  used  as  a  unit  in  all  gas  calculations. 

Two  styles  of  meters  are  used — the  wet  and  the  dry; 
in  the  former  the  gas  passes  .through  a  revolving  drum 
partially  submerged  in  water.  The  revolutions  are  regis- 
tered on  dials  by  appropriate  clockwork.  Since  this 
form  of  meter  is  liable  to  freeze  and  must  always  contain 
water,  some  of  which  is  lost  by  evaporation,  it  has  been 
largely  superseded  by  the  dry  meter,  which  contains  2 
bellows  alternately  full  and  empty.  A  clockwork  de- 
vice, similar  to  that  used  in  the  wet  meter,  keeps  record 
on  appropriate  dials.  Gas  meters  are  subject  to  public 
test  and  are  allowed  an  error  of  2  per  cent,  either  fast 
or  slow. 

Chemical  Changes  During  Combustion. — The  common 
burner  can  only  use  gas  of  the  following  composition: 
methane,  CH4,  ethylene,  C2H4,  acetylene,  C2H2,  hydro- 
gen, H2,  and  carbon  monoxide,  CO.  Combustion  pro- 
ceeds according  to  the  following  equations : 


84  HOUSEHOLD   CHEMISTRY 

CH4  +  2Oa  — •  CO2  +  2H2O  —  heat,  no  light. 

2H2  +  O2  — •>  2H2O  —  heat,  no  light. 

2CO  +  O2  — *  2CO2  —  heat,  no  light. 

C2H4  +  O,  — -  2H2O  +  C,  —  less  heat,  some  light. 

2C2H2  +  O2  —*  2H2O  +  2C2  —  less  heat,  more  light. 

The  Bunsen  burner  mixes  the  gas  with  O2  before 
combustion;  this  affects  only  the  ethylene  and  acetylene 
as  follows: 

C2H4  +  3O,  — >  2H2O  +  2CO2  —  heat,  no  light. 
2C2H,  -4-  50,  — -  2H,O  -f-  4CO,  —  heat,  no  light. 

Acetylene  gas,  C2H2,  is  made  by  the  action  of  water  on 
calcium  carbide  as  follows: 

CaC2  +  2H,O  — -  C,H2  +  Ca(OH)2. 

Calcium  carbide  is  prepared  by  heating  a  mixture  of 
lime  and  charcoal  in  the  electric  furnace. 

Either  the  water  is  sprayed  on  the  carbide,  or  finely 
pulverized  carbide  is  sprinkled  in  water. 

Acetylene  is  only  used  in  places  where  ordinary  gas 
cannot  be  obtained,  and  is  generally  used  at  once.  It 
may,  however,  be  stored  in  an  ingenious  manner:  strong 
copper  cylinders  are  partly  filled  with  acetone,  and  acety- 
lene pumped  in  until  a  certain  pressure  is  obtained.  By 
attaching  one  of  these  tanks  to  a  lamp,  a  strong  light 
may  be  maintained  for  many  hours.  The  rationale  of 
the  process  is  that  acetone  dissolves  acetylene  under 
pressure  and  slowly  gives  it  up  when  the  tension  is  re- 
leased. 

Naphtha  or  Gasoline  Gas. — Many  isolated  country 
houses  depend  for  heat  and  light  on  this  mixture.  Out- 


HOUSEHOLD   CHEMISTRY  85 

side  of  the  building  and  underground,  is  placed  an  iron 
tank  for  holding  the  hydrocarbon ;  pipes  lead  to  and  from 
the  house.  In  the  house  cellar  is  placed  a  large  revolving 
drum  driven  by  weights,  for  forcing  air  through  the 
gasoline  and  driving  back  to  the  house  the  vapor  laden 
air.  The  process  is  satisfactory  on  a  small  scale  but 
rather  expensive,  depending  wholly  on  the  price  of  the 
hydrocarbon. 

Blau  gas  is  the  invention  of  a  German  chemist,  Her- 
man Blau.  It  is  a  mixture  of  hydrocarbons  which  are 
gases  under  ordinary  conditions,  but  which  liquefy  under 
high  pressures  and  low  temperatures  and  are  reconverted 
into  gases  when  the  pressure  is  released.  In  the  making 
of  Blau  gas  ordinary  gas  oil  is  distilled  in  retorts,  the 
mixture  of  gases  produced  is  purified,  cooled  and  com- 
pressed up  to  100  atmospheres.  Hydrocarbons  which 
liquefy  under  these  conditions  will  absorb  others  which 
do  not,  and  also  so-called  permanent  gases  such  as 
methane  and  hydrogen.  The  liquefied  gas  is  delivered 
for  use  in  steel  cylinders  under  high  pressure,  with  a 
device  attached  for  reducing  the  pressure  before  the  gas 
enters  the  service  pipes.  One  cubic  foot  of  the  liquefied 
substance  expands  to  400  cubic  feet  of  gas. 

Pintsch  Gas. — A  similar  method  of  compressing  gas 
was  invented  by  Pintsch.  Under  his  system  the  oil  is 
distilled  at  about  1,000°,  in  order  to  produce  a  large 
amount  of  fixed  gases.  About  80  cubic  feet  of  gas  is 
obtained  from  i  gallon  of  oil.  These  gases  are  stored 
in  receivers  under  a  pressure  ordinarily  of  6  atmos- 


86  HOUSEHOLD   CHEMISTRY 

pheres.     Pintsch  gas  is  widely  used  for  lighting  railway 
cars,  the  receivers  being  carried  underneath  the  car. 

EXPERIMENTS. 

Preparation  of  Methane — In  a  hard  glass  8-inch  test  tube  place 
a  mixture  of  6  grams  of  fused  sodium  acetate  and  4  grams  of 
soda  lime.  Close  with  a  cork  bearing  a  glass  exit  tube.  Heat 
strongly  and  light  the  methane  gas  at  the  mouth  of  the  tube. 
Complete  the  equation : 

CH,COONa  +  NaOH  «~* 

Preparation  of  Ethylene — To  10  cc.  of  H2O  in  a  beaker  slowly 
add  30  cc.  of  concentrated  H2SO«  and  cool.  Put  14  cc.  of 
C'HsOH  in  an  Erlenmeyer  flask,  fitted  with  a  separatory  funnel 
and  a  delivery  tube.  Add  clean  sand  to  prevent  bumping.  Carry 
the  delivery  tube  through  the  cork  of  a  clean,  dry,  12-ounce  or 
i6-ounce  bottle.  Pass  another  delivery  tube  out  of  the  bottle 
and  carry  to  a  pan  for  collecting  gas  over  water.  Slowly  pour 
the  cold  dilute  acid  on  the  alcohol  through  the  funnel,  heat 
gently,  and  collect  I  wide  mouth  bottle  and  2,  narrow  necked 
bottles  of  the  gas.  Test  the  gas  in  the  wide  mouth  bottle  for 
inflammability.  Write  the  reactions  for  the  preparation  of  the 
gas  and  its  combustion. 

Into  one  of  the  narrow  necked  bottles  place  I  cc.  of  bromine 
water,  close  the  bottle  and  shake.  Explain,  note  odor,  and  write 
reaction.  Into  the  second  bottle  put  a  very  dilute  solution  of 
KjMnzOs  and  add  i  cc.  of  10  per  cent.  Na2COs.  Close  and  shake. 
Note  the  change.  Look  up  von  Baeyer's  reaction  for  the  double 
bond. 

Preparation  of  Acetylene,  i.— Drop  a  very  small  lump  of 
calcium  carbide  into  a  test  tube  half  full  of  water.  Light  the 
gas  evolved  and  note  its  illuminating  quality. 

2.  Put  10  grams  of  calcium  carbide  in  an  Erlenmeyer  flask 
provided  with  a  separatory  funnel  and  a  delivery  tube.  Add 
water  drop  by  drop  through  the  funnel  and  collect  the  gas 
evolved  over  water,  in  small  bottles  or  cylinders.  Observe  its 


HOUSEHOLD   CHEMISTRY  87 

inflammability  (Caution:  acetylene  mixed  with  air  is  explosive), 
its  odor,  and  solubility  in  water  and  alcohol.  Test  with  bromine 
water  and  K2Mn2O8  as  under  ethylene.  Write  reactions. 

3.  Collect  some  illuminating  gas  in  bottles  containing  bromine 
water  and  K2Mn2Os  respectively,  as  under  ethylene,  and  shake. 
Note  results.  What  does  this  show  with  regard  to  certain  con- 
stituents of  the  gas? 


CHAPTER  VII. 


CARBOHYDRATES. 

Carbohydrates  are  valuable  organic  compounds  repre- 
senting one  of  the  food  principles.  They  originate  in  the 
development  of  vegetable  life,  being  built  up  in  the  cells 
of  all  chlorophyll-bearing  plants.  These  compounds 
contain  the  elements  carbon,  hydrogen  and  oxygen,  and 
with  some  exceptions  are  aldehyde  or  ketone  alcohols. 
The  term  carbohydrate,  signifying  carbon,  with  hydro- 
gen and  oxygen  in  the  proportion  to  form  water,  has 
lost  its  significance,  for  although  important  members 
of  the  group  conform  to  this  arrangement,  e.  g., 
sucrose  (C^H^O-n),  glucose  (CeHiaO6),  and  starch 
w(C6H10O5),  carbohydrate  bodies  are  known  which  do 
not.  Furthermore,  acetic  and  lactic  acids  which  are  not 
carbohydrates  have  respective  formulas  of  C2H4O2 
and  CsHflOg.  A  better  general  term  is  .saccharids  or 
saccharoses.  The  usual  classification  subdivides  the 
saccharids  as  follows: 

Monosaccharids. — Sugars  which  do  not  hydrolyse  to 
simpler  saccharids.  They  are  alcohols  joined  with  an 
aldehyde  or  a  ketone  group,  and  in  consequence  are 
called  either  aldoses  or  ketoses.  The  number  of  carbon 
atoms  in  the  molecule  is  indicated  by  the  terms  tetrose, 
pentose,  hexose,  etc.,  and  the  full  description  may  be,  for 
example,  aldohexose,  or  ketohexose.  The  hexoses  are 
the  most  important  members  of  this  group. 

Disaccharids. — The  disaccharids  yield  two  monosac- 
charid  molecules  of  the  hexose  type  on  hydrolysis. 


HOUSEHOLD   CHEMISTRY  89 

Trisaccharids. — Raffinose,  the  most  important  example, 
hydrolyses  to  three  hexoses. 

Polysaccharids. — These  bodies  have  large  complex 
molecules  which  hydrolyse  to  an  unknown  number  of 
monosaccharid  molecules. 

The  important  carbohydrates  are  classified  in  detail 
below : 

Classification  and  Occurrence. — 

MONOSACC  H  ARIDS. 

Pentoses,  C5H10O5.  Arabinose,  Xylose,  etc. 

These  do  not  occur  free  in  nature,  but  result 
from   the  hydrolysis   of   polysaccharids   called 
pentosans. 
Hexoses,  C6H12O6. 

Glucose  or  dextrose.  Sometimes  called  grape 
sugar.  Occurs  in  large  amounts  in  grapes,  is 
widely  distributed  in  other  fruits  and  plants, 
and  is  a  product  of  the  hydrolysis  of  most  of 
the  di-,  tri-,  and  polysaccharids.  Normal  blood 
contains  a  small  quantity,  which  is  greatly  in- 
creased in  diabetes. 

Fructose  or  levulose.  Sometimes  called  fruit 
sugar.  Associated  with  glucose  in  nature,  is  a 
large  constituent  of  honey,  and  is  also  a  product 
of  hydrolysis  of  some  carbohydrates. 

Galactose.  Has  no  common  name  and  is  not 
found  free  in  nature.  It  is  obtained  by  the  hy- 
drolysis of  lactose,  raffinose,  and  the  galactans. 


90  HOUSEHOLD   CHEMISTRY 

DlSACCHARIDS. 

The  important  disaccharids  have  the  formula 
C12H22On.  They  are: 

Sucrose.  Known  as  cane,  beet  or  maple 
sugar,  and  found  with  glucose  and  fructose  in 
the  juice  of  many  other  plants. 

Maltose.  The  malt  sugar  of  germinating 
grains.  Also  a  product  commercially  of  the 
partial  hydrolysis  of  starch. 

Lactose.  Known  as  milk  sugar  and  found  in 
the  milk  of  most  mammals. 

TRISACCHARID. 

Raffinose,  Ca8H32O16.  Found  in  the  germ  of  wheat 
and  barley,  in  cotton  seed,  and  usually  in  the  sugar 
beet.  It  is  commonly  extracted  from  the  molasses 
from  beet  sugar. 

POLYSACCHARIDS. 

The  general  expression  wC6H10O5,  n  signifying  that 
the  molecule  is  an  indefinite  multiple  of  the  for- 
mula given,  is  assigned  to  the  hexosans  of  this 
complex  group.  Principal  members  are: 

Starch.  The  most  important  and  widely  dis- 
tributed polysaccharid.  It  occurs  in  plants  gen- 
erally, especially  in  roots,  tubers  and  seeds. 

Dextrin.  Formed  from  starch  by  the  action 
of  heat  alone,  or  by  partial  hydrolysis  with 
enzymes  or  acids.  Found  in  germinating  cereals 
as  a  transition  product. 


HOUSEHOLD    CHEMISTRY  QI 

Glycogen.  Sometimes  called  animal  starch. 
It  is  seldom  found  in  plants,  except  in  certain 
fungi  and  in  varying  amounts  in  yeast.  It 
occurs  in  large  quantities  in  the  liver  of  animals 
and  in  the  muscle  of  the  scallop,  and  in  smaller 
proportion  in  the  blood  and  muscles  generally. 

Cellulose.  Constitutes  the  framework  of  the 
cell  walls  of  all  plant  tissues.  The  cotton  fiber 
is  nearly  pure  cellulose. 

Inulin.  A  starch-like  body  extracted  prin- 
cipally from  dahlia  tubers,  but  found  also  in  the 
artichoke  and  the  roots  of  chicory. 

Galactans.  Occur  in  the  seeds  of  legumes; 
yield  galactose  on  hydrolysis. 

Pentosans.  (CjHgO^)*.  Araban  and  xylan, 
yielding  arabinose  and  xylose  on  hydrolysis. 
Widely  distributed  in  nature,  especially  in  such 
substances  as  bran,  wood,  straw,  etc.  No  con- 
siderable amount  in  food  material. 

Natural  Gums.  Bodies  which  are  generally 
classed  with  the  polysaccharids,  but  the  com- 
position of  many  of  which  is  not  definitely 
known.  Pectin  bodies  belong  to  this  group. 

Photosynthesis. — In  the  presence  of  sunlight  the  chloro- 
phyll-bearing plant  cell  takes  carbon  dioxide  from  the 
air,  combines  it  with  water,  and  polymerizes  the  product 
into  a  carbohydrate  body.  This  photosynthesis  may  be 
represented  by: 

6CO,  -f  6H,O  •—  C6H13O,  +  6Oa. 

7 


92  HOUSEHOLD   CHEMISTRY 

Such  an  expression  does  not  take  into  account  the  inter- 
mediate products  of  the  synthesis,  about  which  more  has 
to  be  learned.  Baeyer,  Erlenmeyer  and  others  theorize 
that  the  carbon  dioxide  and  water  undergo  double  decom- 
position, and  formaldehyde  is  formed  and  synthesized  to 
a  monosaccharid,  according  to  the  reactions : 

CO,  +  H2O  —  HCHO  +  O2, 
6HCHO  ~->  C6H12O6. 

The  theory  is  supported  by  the  fact  that  formaldehyde 
has  been  found  in  plant  cells,  and  that  it  can  be  po- 
lymerized to  fructose.  According  to  Asher  and  Priestly, 
hydrogen  peroxide  is  also  produced  in  the  above  change, 
but  is  quickly  decomposed  to  water  and  oxygen  by  a  cata- 
lase  in  the  leaf. 

Hydrolysis. — By  enzyme  action  in  the  plant  or  animal 
body,  or  by  the  action  of  dilute  acids  and  heat,  di-  and 
polysaccharids  are  hydrolyzed.  The  hydrolysis  of  a  few 
of  the  important  saccharids  is  given : 

Enzymes.  Products. 

(Equal  parts  of 
glucose  and  fruc- 
tose (invert  sugar). 

•RT  14.  *,  u  J      Two  molecules  of 

Maltose  {  glucose. 

f      Equal   parts  of 

Lactose  lactase  -j  glucose  and  galac- 

(  tose. 

Starch  amylases  f      Dextrins    and 

Glycogen  ( ptyalin  diastase          •]  maltose, 

etc.)  I 

Raffinose  is  hydrolyzed  by  strong  mineral  acids  to  a 
molecule  each  of  glucose,  fructose,  and  galactose.  Inulin 


HOUSEHOLD   CHEMISTRY  93 

is  easily  changed  by  acid  hydrolysis  to  fructose;  it  is  not 
ordinarily  attacked  by  enzymes.  Cellulose  and  starch  are 
considered  anhydrides  of  glucose,  and  both  yield  glucose 
on  acid  hydrolysis.  Ordinary  cellulose  is  not,  however, 
hydrolyzed  by  amylases  or  other  enzymes,  but  by  bac- 
terial action. 

The  hydrolysis  of  pectic  bodies  is  complex,  and  the 
cleavage  products  not  definitely  known.  A  substance  is 
found  associated  with  cellulose  in  the  cell  walls  of  unripe 
fruits  to  which  the  name  pectose  is  given.  As  the  fruit 
ripens,  pectose  is  converted  by  enzyme  action  into  pectin. 
This  change  can  be  brought  about  by  boiling  pectose  with 
dilute  acids  or  caustic  alkalies,  and  the  products  include 
not  only  pectin  in  several  forms  but  a  number  of  acids. 
Pectin  has  the  power  of  swelling  in  water  and  gelatiniz- 
ing, a  property  of  which  advantage  is  taken  in  jelly 
making.  (See  Chap.  VIII.) 

In  household  practice  many  examples  of  hydrolysis 
occur,  e.  g.,  when  starch  and  sugar  are  cooked  with  fruit 
acids ;  in  the  process  of  caramelizing  sugar  or  in  making 
fondant.  Sugar  hydrolyzes  much  more  quickly  than 
starch. 

Optical  Activity. — Nearly  all  carbohydrates  are  op- 
tically active.  Pure  sucrose  has  a  right  rotation  of  66° ; 
its  hydrolytic  products,  glucose  and  fructose,  show  muta- 
rotation,  but  the  average  figure  for  dextro-glucose  is 
-j-  52.5°,  that  for  fructose  or  levulose  is  —  93-8°.  Since 
the  pull  of  fructose  to  the  left  is  greater  by  41.3°  than 
that  of  glucose  to  the  right,  it  can  be  seen  that  an  equal 


94  HOUSEHOLD   CHEMISTRY 

mixture  of  the  two  would  have  a  left  rotation,  opposite 
to  that  of  sucrose.  For  this  reason  the  name  invert 
sugar  is  given  to  the  hydrolytic  products  of  sucrose.  A 
practical  application  of  this  is  made  in  the  use  of  the 
saccharimeter  (q.  v.),  by  means  of  which  the  purity  of 
cane  sugar  is  determined  by  estimating  the  amount  of  in- 
vert it  may  contain. 

Solubility. — The  mono-  and  disaccharids  are  soluble  in 
water.  Of  the  polysaccharids,  starch  is  not  soluble  in 
cold  water,  but  in  hot  water  the  granules  burst  and  the 
contents  become  a  gelatinous  mass  known  as  starch 
paste.  Dextrin  is  soluble  in  cold  water,  more  readily  in 
hot ;  glycogen  dissolves  with  an  opalescent  appearance ; 
cellulose  is  not  soluble  in  either  hot  or  cold  water.  In 
strong  alcohol  the  monosaccharids  are  sparingly  soluble ; 
of  the  disaccharids  maltose  dissolves  most  readily,  sucrose 
to  a  limited  extent,  lactose  is  almost  insoluble.  All  the 
polysaccharids  are  insoluble. 

General  Reactions. — Molisch's  Test. — All  carbohydrates 
respond  to  Molisch's  reagent.  To  about  3  cc.  of  a  dilute 
solution  of  any  carbohydrate  add  2  or  3  drops  of 
Molisch's  reagent,  mix  thoroughly,  and  carefully  pour 
concentrated  H2SO4  down  the  inclined  side  of  the  test 
tube.  A  violet  ring  appears  at  the  contact  surface  of  the 
liquids. 

Furfural. — All  carbohydrates  yield  some  furfural  on 
treatment  with  boiling  HC1;  the  pentoses  are  distin- 
guished by  the  formation  of  large  amounts. 

Ultimate  Composition — i.  Determination  of  Hydrogen  and 
Oxygen  Evolved  as  Water. — Heat  about  i  gram  of  granulated 


HOUSEHOLD    CHEMISTRY  95 

sugar  in  a  clean  dry  test  tube.    Observe  the  condensation  of 
moisture  in  the  cooler  part  of  the  tube. 

2.  Determination     of    Carbon. —  (a)   By    dehydration.      Treat 
about  i  gram  of  the  sugar  in  a  porcelain  evaporating  dish  with 
a  little  concentrated  sulphuric  acid,  heat  gently  and  note  the 
blackening  effect.    In  this  case,  the  concentrated  sulphuric  acid 
withdraws  the  hydrogen  and  oxygen  in  the  form  of  water  and 
leaves  the  carbon.     (6)  By  direct  heat;  continue  heating   (Ex- 
periment i)  and  note  the  blackening  of  the  mass  due  to  freeing 
of  some  of  the  carbon. 

3.  Determination  of  Hydrogen  and  Carbon  in  the  Form  of 
Hydrocarbons,  i.  e.,  Tarry  Bodies. — Observe  the  pungent  odor  of 
the  vapors  arising  from  the  tube  during  the  heating  in  experi- 
ment 2  (&).    These  usually  condense  on  the  cooler  part  of  the 
tube  in  the  form  of  a  dark  brown  liquid   (caramel). 

Glucose. 

Preparation. — Glucose  is  prepared  commercially  in  the 
United  States  by  hydrolysing  starch  with  dilute  hydro- 
chloric acid  under  pressure,  neutralizing  with  soda  ash, 
and  evaporating  the  product  in  vacuum  pans.  It  is  sold 
in  syrup  and  in  crystal  form.  Commercial  glucose  con- 
tains varying  amounts  of  dextrin.  By  carrying  the  hy- 
drolytic  action  further,  pure  glucose  or  grape  sugar  may 
be  produced. 

Constitutional  Structure. — That  glucose  is  an  aldo- 
hexose  is  proved  by  its  reactions.  The  structural  for- 
mula usually  assigned  to  it  is  CH2OH  (CHOH)4  CHO. 
The  space  configuration  shown  on  next  page  illustrates 
the  isomeric  differences  between  glucose  and  the  other 
important  hexoses : 


HOUSEHOLD   CHEMISTRY 


OH— 
OH- 

H— 
OH— 


CH,OH 


CH,OH 


— H 
— H 
—OH 
-H 


OH— 

OH— 

H— 

H— 


— H 
— H 
—OH 
—OH 


OH- 

OH- 

H— 


CH,OH 
— H 


— H 
—OH 


CO 

I 


CH3OH 

d—  fructose 


CHO  CHO 

d— glucose  d — galactose 

Properties. — Glucose  is  crystalline,  soluble  and  diffu- 
sible. It  crystallizes  with  difficulty  from  water,  more 
readily  from  alcohol.  In  the  first  case  the  crystals  ap- 
pear as  thin  plates  in  amorphous  masses,  usually  contain- 
ing water  of  crystallization.  Anhydrous  needle  or  prism 
crystals  may  be  obtained  from  alcohol. 

Nearly  all  yeasts  readily  ferment  glucose,  producing 
for  the  most  part  alcohol  and  carbon  dioxide:  C6H12O6 
— >  zCO,  +  2C2H5OH. 

Reducing  Power. — Glucose  shows  its  aldehyde  charac- 
ter in  its  power  of  reducing  metallic  solutions  such  as 
are  found  in  Fehling's,  Barfoed's  or  Nylander's  reagents, 
or  alkaline  silver  nitrate.  In  the  last  a  deposit  of  silver 
is  formed ;  in  Fehling's  and  Barfoed's  the  reduction  from 
a  higher  to  a  lower  copper  oxide  is  shown  by  a  color 
change  from  blue  to  red.  Fehling's  solution  is  the  one 
most  commonly  used  to  determine  the  presence  of  a  re- 
ducing sugar.  The  reactions  taking  place  in  changing 
from  the  cupric  hydroxide  to  the  cuprous  oxide  may  be 
briefly  indicated  as  follows: 

2Cu(OH)a  -~  2CuOH  +  H,O  +  O. 
Blue  Yellow 

2CuOH  — *  Cu2O  +  H2O. 
Red 


HOUSEHOLD   CHEMISTRY  97 

The  reduction  of  Fehling's  by  glucose  may  be  made 
quantitative,  50  milligrams  of  glucose  reducing  10  cc. 
of  the  standard  solution. 

Formation  of  Osazone. — With  phenylhydrazine  glucose 
forms  yellow  needle  crystals  of  phenylglucosazone, 
which  are  an  identification  test  for  this  .sugar.  The 
change  involves  several  reactions,  in  the  first  of  which 
a  hydrazone  is  formed : 

CH2OH(CHOH)4CHO  +  NH2NHC6H5  — 
Glucose  Phenylhydrazine 

CHJOH(CHOH),CH:N.NHC6H5  +  H2O. 
A   second   reaction  takes   place,   more  phenylhydrazine 
acting  as  an  oxidizing  agent  on  the  adjacent  =  CHOH 
group: 

=  CHOH  +  NHjNHC.H,  — » 

=  CO  +  NH,  +  NH,C8H6. 

The  CO  left  forms  a  second  hydrazone  group  with  phen- 
ylhydrazine present,  the  product  being  called  an  osazone, 
in  this  case  phenylglucosazone: 

CH2OH(CHOH)SCOCHNNHC6H6  -f  NH2NHC6H5  -~ 
CH2OH(CHOH),C:N.NHC6H6CH:N.NHC,H5. 

Action  of  Acids  and  Alkalies. — When  boiled  with  strong 
HC1,  glucose  is  oxidized  to  levulinic  acid,  CH3COCH2 
CH2COOH;  with  nitric,  to  saccharic  acid  COOH 
(CHOH)4COOH.  If  heated  with  strong  caustic  soda 
or  potash  a  series  of  complex  reactions  of  an  oxidative 
nature  take  place,  and  a  brown  color  results.  All  car- 
bohydrates with  a  free  carbonyl  group  give  this  reaction. 


98  HOUSEHOLD   CHEMISTRY 

EXPERIMENTS  ON  GLUCOSE. 

1.  Taste,  and  note  the  sweetness.     (Glucose   is  about  three- 
fifths  as  sweet  as  cane  sugar.)     Roughly  determine  its  solubility 
in  hot  and  cold  water  and  in  alcohol.    Does  it  react  with  iodine? 

2.  Effect   of   Heat — Heat   some   dry   glucose   in   a   clean   dry- 
test  tube,  note  the  result. 

3.  Effect  of  Strong  Acid. — To  some  dry  glucose  in  a  porcelain 
dish  add  cold  concentrated  sulphuric  acid :  note  the  result.    After 
allowing  the  test  to  stand  for  5  minutes,  heat  gently  and  again 
note  the  result. 

4.  Effect   of    Strong   Alkali — To    some   glucose    solution   add 
strong  caustic  soda  or  potash  and  heat;  note  the  result. 

5.  Crystallization — Make   a   syrupy   solution   of    glucose   and 
allow  it  to  stand  for  several  days.    Do  any  crystals  form? 

6.  Fermentation. — Combine  equal  portions  of  compressed  yeast 
with  solutions  of  glucose,  lactose,  maltose  and  sucrose  of  equal 
strength,  and  starch  paste.    Fill  the  long  arm  of  five  bulb  fer- 
mentation tubes  with  the  five  mixtures  and  close  the  bulb  with  a 
cotton  plug.    Stand  in  a  warm  place  until  fermentation  begins. 
In  each  case  note  the  rapidity  with  which  carbon  dioxide  rises 
in  the  long  arm  of  the  tube  and  presses  the  liquid  into  the  bulb, 
and  draw  conclusions  as  to  the  comparative  action  of  yeast  on 
the  four  sugars  and  the  starch.     Examine  the  liquid  in  the  bulb 
for  alcohol  by  (i)  taste,  and   (2)  heating  with  a  small  amount 
of  iodine  and  sodium  carbonate  solution. 

7.  Fehling's  Solution  Test — In  a   100  cc.  flask  take  5  cc.  of 
copper  sulphate  solution  and  5  cc.  of  alkaline  Rochelle  salt,  max 
and  add  20  cc.  of  distilled  water,  cover  with  a  watch  crystal  and 
boil  for  2  minutes.    No  change  should  take  place.    Add  a  few 
drops  of  glucose  solution,  boil  vigorously  for  2  minutes,  cool 
and  note  the  result.     Continue  adding  glucose  and  boiling  until 
on  cooling  the  blue  color  of  the  solution  has  faded  and  a  red 
precipitate  is  formed. 

NOTE:    The  solution  under  test  must  be  neutralized  if  acid, 


HOUSEHOLD   CHEMISTRY  99 

as  acids  destroy  the  necessary  alkaline  condition  of  Fehling's  and 
act  in  some  degree  as  reducing  agents. 

8.  Barfoed's  Solution — Add  a  few  drops  of  glucose  solution 
to  a  small  amount  of  Barfoed's  in  a  test  tube,  place  the  tube  in 
boiling  water  for  a  few  moments.    A  clear  red  precipitate  ap- 
pearing around  the  edges  of  the  liquid  indicates  reduction  to 
cuprous  oxide.     Barfoed's  is  an  acid  preparation — the  test  solu- 
tion added  to  it  must  not  be  alkaline. 

9.  Silver  Mirror  Test — To   illustrate   the   reducing   action  of 
glucose  on  silver  nitrate  make  a  silver  mirror  as  follows :     Clean 
the  article  to  be  silvered — either  a  watch  crystal  or  a  small  test 
tube — with  nitric  acid,  water,  and  strong  alcohol  in  the  order 
mentioned,  and  place  in  contact  with  hot  water.     Make  a  strong 
solution  of  glucose.    Take  sufficient  5  per  cent.  AgNOa  to  fill 
the  article,  add  ammonia  cautiously  until  the  precipitate  formed 
almost  disappears  on  shaking,  then   i   or  2  cc.  of  the  glucose 
solution.    Mix  quickly  and  fill  the  glass  receptacle.    When  the 
reduction  to  metallic  silver  seems  complete,  pour  off  the  solution. 

10.  Preparation  of  Phenylglucosazone — To  0.2  gram  of   pure 
glucose  dissolved   in  4  cc.  of  water,   add  0.4  gram  of  phenyl- 
hydrazine   hydrochloride,   and   0.6  gram   of   crystallized   sodium 
acetate.    Filter  the  solution  if  not  clear,  close  the  test  tube  with 
a  cotton  plug,  warm  in  a  water  bath  until  yellow  crystals  of 
phenylglucosazone  appear.    Observe  these  under  a  microscope. 

Glucosides. — These  are  complex  substances  found  in 
the  vegetable  kingdom,  which  on  hydrolysis  yield  a  car- 
bohydrate— generally  glucose — and  one  or  more  other 
compounds.  Many  glucosides  are  known,  together  with 
the  hydrolyzing  enzymes  which  usually  accompany  them 
in  the  plant.  A  well  known  example  is  amygdalin,  found 
in  bitter  almonds,  and  the  kernels  of  peaches,  cherries, 
plums,  etc.  It  is  hydrolyzed  by  the  emulsin  of  almonds 
to  glucose,  benzaldehyde,  and  hydrocyanic  acid.  Phlor- 


IOO  HOUSEHOLD   CHEMISTRY 

idzin  is  found  in  the  root  bark  of  apple,  pear,  plum  and 
cherry  trees,  and  yields  glucose  and  phloretin  by  acid 
hydrolysis. 

Fructose. 

The  occurrence  of  fructose  or  levulose  in  nature  has 
been  given,  also  its  space  configuration  (p.  96).  The 
term  d-fructose  does  not  indicate  the  direction  of  its 
rotation  of  polarized  light,  which  is  left-handed,  but  its 
derivation  from  d-glucose.  L-fructose  turns  polarized 
light  to  the  right,  being  the  mirror  image  of  d-fructose. 

Fructose  is  harder  to  crystallize  than  glucose,  but 
forms  fine  rhombic  needles.  It  is  somewhat  sweeter  than 
cane  sugar. 

Reactions. — i.  Resorcin  gives  a  characteristic  color  re- 
action with  fructose,  due  to  the  ketohexose  nature  of 
the  latter.  Carbohydrates  such  as  cane  sugar  which 
yield  fructose  on  hydrolysis,  also  give  this  reaction. 

Mix  equal  volumes  of  hydrochloric  acid  and  fructose  solution 
and  add  a  few  drops  of  resorcin  solution.  Warm;  notice  a  deep 
red  color  and  the  formation  of  a  brownish  precipitate. 

2.  Substances  which,  like  fructose,  have  a  ketone  rad- 
ical linked  to  a  =  CHOH  group,  act  as  reducing  agents 
in  alkaline  solutions  such  as  Fehling's. 

3.  Milk  of  lime  precipitates  fructose  as  an  insoluble 
calcium  compound,  and  thus  can  be  used  to  separate  the 
constituents  of  invert  sugar,  since  the  glucose  remains  in 
solution. 

EXPERIMENT. 
Dissolve  50  grams  of  pure  honey  in  250  cc.  of  water,  cool 


HOUSEHOLD    CHEMISTRY  IOI 

with  ice,  and  add  30  grams  of  slaked  lime  in  small  quantities, 
stirring  constantly.  Filter  off  the  precipitate,  wash  it  with  a 
little  water,  press  strongly  to  remove  excess  liquid,  suspend 
it  in  water  and  pass  a  stream  of  carbon  dioxide  through  the 
mixture.  The  lime  compound  of  fructose  is  decomposed.  What 
precipitates?  Filter,  and  evaporate  the  fructose  in  the  filtrate 
to  a  syrup.  Test  with  Fehling's  and  resorcin. 

If  invert  sugar  is  used  for  the  above  experiment  de- 
crease the  amount  to  ]/$. 

4.  With  phenylhydrazine  fructose  gives  an  osazone 
identical  with  phenylglucosazone. 

Fructose  may  be  obtained  by  extracting  inulin  from 
dahlia  tubers  and  hydrolyzing  it. 

EXPERIMENT. 

Grate  several  dahlia  tubers,  suspend  the  gratings  in  water, 
filter  through  muslin,  collect  the  inulin  as  it  settles  at  the 
bottom  and  mix  with  water.  Heat  this  aqueous  mixture  on 
a  water  bath  for  an  hour,  with  a  few  drops  of  H2SO4  as  the 
hydrolyzing  agent.  Neutralize  with  barium  hydroxide,  filter,  and 
evaporate  the  filtrate  at  low  heat  to  a  syrup.  Apply  tests  given 
above  for  fructose. 

Galactose. 

Galactose  is  an  aldose,  which  is  not  found  in  the  free 
state,  but  can  be  prepared  by  hydrolyzing  lactose  and 
separating  the  products,  glucose  and  galactose,  by  crys- 
tallization of  the  latter  from  aqueous  alcohol.  It  crys- 
tallizes in  prisms  which  melt  at  168°.  Galactose  is 
mutarotatory,  with  an  equilibrium  value  of  +81°.  With 
phenylhydrazine  it  forms  a  compound  similar  to  glucose. 
Galactose  is  fermentable,  but  not  by  ordinary  yeast. 


102  HOUSEHOLD   CHEMISTRY 

Sucrose. 

Sucrose  is  an  alcohol,  with  no  free  aldehyde  or  ketone 
group,  as  is  shown  by  its  formula: 

CHaOH  CH.OH 


CHOH 

,  —  CH 

i 

,  CH 

CHOH 

O      | 

CHOH 

~v 

CHOH 

i 

CHOH 

'  C 

L       OTT 

JTt/      PTT  OTT 

It  therefore  does  not  act  as  a  reducing  agent  when  pure. 
Chemically,  it  is  identical  whether  produced  from  cane, 
beets,  or  maple  sap.  It  crystallizes  easily  into  large  octo- 
hedrons,  and  is  the  most  readily  soluble  in  water  of  all 
the  carbohydrates.  In  strong  alcohol  it  is  scarcely  solu- 
ble. Sucrose  hydrolyzes  readily  with  acids  and  even 
with  heat  alone.  In  the  latter  case  the  product  is  called 
caramel,  and  the  beginning  of  the  inversion  corresponds 
with  the  first  yellowing  of  the  sugar. 

Saccharimeter  Test. — The  purity  of  cane  sugar,  i.  e.,  its 
freedom  from  invert,  is  determined  by  a  modification  of 
the  polariscope  called  a  saccharimeter.  In  one  type  of 
the  instrument,  using  the  Ventzke  scale,  the  light  passes 
through  the  polarizer,  from  that  through  the  tube  con- 
taining the  sugar  solution,  and  then  through  the  analyzer. 
This  is  a  pair  of  quartz  wedges  arranged  to  neutralize 


HOUSEHOLD   CHEMISTRY  IO3 

the  rotating  effect  of  the  sugar,  and  at  the  same  time 
record  the  degree  of  rotation  on  a  scale.  The  rotating 
effect  of  pure  sugar,  -f-  66°,  is  read  as  100  per  cent,  on 
the  scale;  a  reading  of  less  than  100  per  cent,  indicates 
impurity,  and  the  amount  of  invert  present  can  be  cal- 
culated. 

For  the  saccharimeter  test  (using  the  Ventzke  scale) 
26  grams  of  cane  sugar  are  dissolved  in  the  least  quantity 
of  water  and  made  up  to  100  cc.  The  solution  must  be 
clear  and  colorless.  In  case  it  is  not,  the  color  may  be 
discharged  by  means  of  a  solution  of  basic  acetate  of 
lead,  which  precipitates  dextrin  and  gummy  matter,  and 
by  bone-black,  which  removes  soluble  coloring  matter. 
The  operation  is  conducted  as  follows :  26  grams  of 
sugar  are  dissolved  in  somewhat  less  than  100  cc.  water, 
a  few  cc.  (not  more  than  five)  of  the  lead  solution  are 
added  and  the  solution  diluted  to  mark.  The  mixture 
is  shaken  vigorously  and  then  allowed  to  stand  for  a  few 
minutes  for  the  bulky  precipitate  to  settle.  If  perfectly 
clear  and  colorless,  the  liquid  is  poured  into  the  tube;  if 
the  color  has  not  entirely  been  removed  a  subsequent 
treatment  with  alumina  cream  is  necessary.  For  this 
purpose  not  more  than  5  cc.  of  freshly  prepared  alumina 
cream  are  added  to  the  liquid,  the  mixture  is  well  shaken 
and  allowed  to  stand  for  the  precipitate  to  settle.  The 
mixture  is  then  filtered  through  dry  paper,  the  first  10  cc. 
of  the  filtrate  being  rejected.  It  may  be  necessary  to 
refilter  through  the  same  paper  two  or  three  times.  The 
tube  of  the  instrument  is  then  filled  with  the  solution, 


104  HOUSEHOLD   CHEMISTRY 

the  rotating  effect  determined,  and  the  percentage  of 
purity  read  on  the  scale. 

EXPERIMENTS  ON  SUCROSE. 

1.  Roughly  determine  its  solubility  in  cold  and  hot  water,  and 
in  alcohol.     Is  the  solubility  affected  by  heat? 

2.  Crystallization — Make  a  hot  syrupy  solution  of  sugar  and 
suspend  in  it  a  piece  of  glass  rod  by  a  thread.    Set  aside  and 
allow  to  cool  and  after  a  time  carefully  examine  the  crystals  of 
cane  sugar. 

3.  Effect  of  Dry  Heat — Boil  down  sugar  solution  to  dryness 
and  note  the  result. 

4.  Effect  of  Strong  Acid. — Drop  some  concentrated  sulphuric 
acid  on  dry  sugar,  note  the  result  and  compare  with  starch  and 
glucose. 

5.  Boil  weak  sugar  solution  with  Fehling's  solution.    If  pure 
there  should  be  no  reduction. 

6.  Hydrolysis.— "Inversion."_Boil   sugar   solution   with  a   few 
drops   of   concentrated  hydrochloric  acid,   cool,   neutralize   with 
sodium  carbonate  and  heat  again  with  Fehling's  solution;  note 
the  result  and  compare  with  glucose.    What  change  has  taken 
place  ? 

7.  Test  hydrolyzed  and  unhydrolyzed  sugar  solution  with  Bar- 
foed's. 

8.  Effect  of  Strong  Alkali — To  10  cc.  of  sugar  solution  add 
some  strong  caustic  soda,  heat  and  note  the  result ;  compare  with 
glucose. 

9.  Specific  Test — To  15  cc.  of  the  clear  liquid,  add  5  cc.  of 
cobalt  chloride  (5  per  cent.)  and  2  cc.  of  caustic  soda  (50  per 
cent.).    Sucrose  gives  an  amethyst-violet,  permanent  on  heating. 
Glucose  gives  a  turquoise-blue,  turning  to  green  on  standing  some 
time,  or  on  gentle  heating.    This  test  may  be  used  on  condensed 
milk,  honey,  preserves,  etc. 

10.  Caramel  Test — Boil  a  strong  solution  of  sugar  until  it  has 
turned  brown  (caramel),  cool,  dilute  and  test  some  of  the  liquid 
with  Fehling's  solution. 


HOUSEHOLD   CHEMISTRY 


105 


11.  Saccharimeter  Test — Determine  the  purity  of  samples  of 
cane  sugar  by  the  saccharimeter. 

12.  Formation  of  Sucrosate — Sucrose  unites  with  metallic  hy- 
droxides such  as  calcium  and  barium  to  form  sucrosates.    Cal- 
cium sucrosate  may  be  prepared  by  saturating  lime  water  with 
cane  sugar  at  low  heat.    The  product  is  commonly  called  vis- 
cogen,  and  is  used  as  a  thickener  in  whipping  cream,  etc. 

13.  Resorcin  Test — To  a  solution  of  cane-sugar  add  an  equal 
volume   of   HC1   and   a   few   crystals   of    resorcin.    Warm.    A 
deep  red  color  appears,  due  to  the  formation  of  fructose. 

Maltose. 

Maltose  does  not  occur  in  nature,  but  is  produced 
during  the  hydrolysis  of  starch  by  unorganized  ferments, 
such  as  ptyalin  and  diastase.  It  is  an  aldose,  as  is  shown 
by  its  formula: 

CH2OH   , — CH, 


O 


CHOH 

I 
— CH 

CHOH 
CHOH 


CHOH 
6  CHOH 
CHOH 
CHOH 


i CH 1   CHO 

On  hydrolysis  maltose  yields  two  molecules  of  glucose: 

H2O 

C12H220U  -~  2C6H1206. 

Maltose  is  readily  soluble  in  water  and  crystallizes 
from  it  in  fine  plates  in  the  hydrated  form  C^H^On, 
H2O.  It  becomes  anhydrous  by  drying  at  100°.  In  the 
hydrated  state  it  dissolves  more  freely  in  alcohol  than  do 


106  HOUSEHOLD   CHEMISTRY 

sucrose  and  lactose,  and  in  this  way  also  can  be  separated 
from  its  mixture  with  most  dextrins,  which  are  precip- 
itated by  alcohol  of  over  60  per  cent  strength. 

With  phenylhydrazine,  yellow  crystals  of  phenylmalt- 
osazone  form  which  resemble  irregular  daisy  petals  or 
knife  blades. 

The  maltase  in  ordinary  brewer's  yeast  acts  readily  on 
maltose,  hydrolyzing  it  to  glucose. 

It  requires  80  milligrams  of  maltose  to  reduce  Feh- 
ling's,  against  50  milligrams  of  glucose. 

EXPERIMENTS  ON  MALTOSE. 

Preparation  of  Diastase  in  the  Form  of  Malt. — Malt  is  produced 
during  the  germination  of  barley  and  other  cereals.  Prepare 
it  as  follows :  Spread  out  a  thin  layer  of  barley  grains  (one 
tablespoon ful)  on  the  cover  of  a  small  pasteboard  box,  moisten 
with  warm  water  and  keep  in  a  moderately  warm  place.  Each 
grain  will  soon  begin  to  sprout.  When  the  rootlet  has  grown  the 
length  of  the  grain,  dry  it  in  an  oven  at  a  low  temperature  and 
keep  bottled.  Make  malt  extract  by  grinding  the  grains  coarsely 
and  extracting  them  with  100  cc.  of  warm  water.  Note  the 
taste  and  odor  of  the  liquid.  Keep  for  future  use. 

Preparation  of  Pure  Maltose — Make  a  thin  paste  of  starch  and 
boiling  water,  cool  to  65°  and  add  10  cc.  of  malt  extract, 
prepared  as  above,  and  continue  the  heating  at  65°  for  half 
an  hour.  From  time  to  time  test  small  portions  of  the  liquid 
with  iodine  solution.  When  the  liquid  fails  to  react  blue,  cool 
the  balance  of  the  solution  divide  in  6  parts  and  test  as  follows : 

1.  Solubility  in  Alcohol — Add   some  of   the  liquid  to  strong 
alcohol,  allow  to  stand  and  note  the  white  precipitate  of  dex- 
trin:  the  liquid  contains  maltose. 

2.  Effect  of  Fehling's  Solution. — To  10  cc.  of  Fehling's  solution 
add  a  few  drops  of  the  liquid,  boil  for  2  minutes  and  note  the 


reduction;  add  more  of  the  solution  and  boil  again;  repeat  until 
the  reduction  is  complete. 

3.  Test  with  Barfoed's  reagent. 

4.  Apply  the  fermentation  test. 

5.  Test  with  strong  caustic  soda  or  potash. 

6.  Repeat  the  phenylhydrazine  test.     Compare  with  glucose. 
NOTE. — The  above  tests  may  be  made  on  commercially  pre- 
pared maltose. 

Lactose. 

Lactose,  or  milk  sugar,  is  a  disaccharid  containing  a 
free  carbonyl  group.  The  structural  formula  for  malt- 
ose (q.  v.)  may  be  used  to  represent  lactose  also.  It  is 
a  reducing  agent,  67.8  milligrams  being  required  to  re- 
duce completely  10  cc.  of  Fehling's. 

Lactose  is  less  soluble  in  water  than  sucrose  or  maltose. 
Five  or  six  parts  of  cold  water  are  required  for  solution, 
or  about  two  and  one-half  parts  of  boiling  water.  When 
crystallized  from  water  at  low  temperature  it  contains 
one  molecule  of  water  of  crystallization,  which  is  lost  by 
heating  the  crystals  to  130°.  Lactose  is  insoluble  in 
alcohol. 

With  phenylhydrazine  yellow  crystals  of  phenyl-lact- 
osazone  are  formed,  which  resemble  chestnut  burrs. 
Ordinary  yeast  does  not  ferment  lactose,  but  lactic 
ferments  convert  it  into  lactic  acid  and  alcohol.  It 
readily  undergoes  butyric  acid  fermentation  also. 

Lactose  is  hydrolyzed  by  lactase  or  by  dilute  mineral 
acids  to  a  molecule  each  of  glucose  and  galactose. 

EXPERIMENTS  ON  LACTOSE. 

Preparation — Allow   milk  to   stand   until   well   soured ;   filter. 
Faintly  acidulate  the  whey  with  dilute  acetic  acid  and  heat  to 
8 


108  HOUSEHOLD   CHEMISTRY 

coagulate   protein   material.     Filter,   and   evaporate   the   filtrate 
over  hot  water  to  crystallization.    The  crystals  are  crude  lactose. 
Take  some  of  the  lactose  so  prepared,  or  the  commercial  form, 
and  make  the  following  tests : 

1.  Note  the  hardness   and   slightly   sweet  taste,   due  to  the 
limited  solubility. 

2.  Try  its  solubility  in  water  and  in  alcohol. 

3.  Treat   some  dry  powdered   lactose   with   concentrated   sul- 
phuric acid,  note  the  result. 

4.  Try  the  caustic  soda  reaction. 

5.  Apply  the  Fehling's  test. 

6.  Test  with  Barfoed's  reagent. 

7.  Make  a  weak  solution  of  lactose  in  water,  let  k  stand  at 
least  24  hours  in  a  moderately  warm  place,  and  then  test  for 
acidity. 

8.  Make  the  phenylhydrazine  test,  compare  with  glucose  and 
maltose. 

Starch. 

Starch  is  the  most  widely  distributed  carbohydrate. 
It  is  found  in  varying  proportions  in  leaves,  stems, 
woody  tissues,  roots,  tubers,  fruits  and  seeds,  but  is  es- 
pecially abundant  in  the  cereal  grains  and  in  tubers  such 
as  the  potato.  The  formula  «(C6H10O5)  is  used  to  ex- 
press its  large  and  complex  molecule,  but  soluble  starch — 
or  its  principal  constituent,  amylo-dextrin — is  sometimes 
represented  as  (C12Ho0O1())54. 

Physical  State. — Pure  starch  is  a  white,  powdery  sub- 
stance, colloidal  and  granular.  The  granules  are  definite 
in  average  size  and  appearance  according  to  their  source. 
Potato  starch  has  one  of  the  largest  granules.  They 
are  ovoid  in  shape,  and  show  concentric  layers  which  in- 
crease in  thickness  with  their  distance  from  the  nucleus 


HOUSEHOLD   CHEMISTRY  ICX) 

or  hilum.  The  size  increases  with  age.  The  outer  layer 
of  starch  granules  is  known  as  starch  cellulose;  the  con- 
tents as  granulose  or  amylose. 

Effect  of  Heat. — In  hot  water  the  outer  layer  of  starch 
granules  is  ruptured  and  the  contents  gelatinize,  form- 
ing a  partial  solution  known  as  starch  paste.  The  tem- 
perature of  gelatinization  varies  from  65°  to  85°,  ac- 
cording to  the  kind  of  starch.  Root  and  tuber  starches 
gelatinize  at  a  lower  temperature,  as  a  rule,  than  cereal 
starches.  According  to  some  investigators1  gelatinization 
is  caused  by  a  mucilaginous  substance,  amylo-pectin, 
found  in  the  granule.  This  body  does  not  give  the  iodine 
reaction,  and  swells  without  dissolving  in  hot  water. 

Ordinary  air-dried  starch  is  dextrinized  at  temperatures 
from  1 60°  to  210°.  Reducing  sugars  may  possibly  be 
formed.  With  higher  temperatures,  and  out  of  contact 
with  air,  starch  yields  products  similar  to  those  formed 
in  the  dry  distillation  of  wood. 

Effect  of  Low  Temperature. — On  cooling,  starch  paste 
contracts.  Its  greatest  contraction  is  at  freezing  point, 
when  a  permanent  separation  of  water  and  starch  takes 
place  to  a  considerable  extent,  and  the  starch  dries  out 
as  a  powdery  mass.  This  substance  is  often  noticed  on 
starched  clothes  dried  after  being  frozen,  and  such 
clothes  have  lost  most  of  their  stiffness. 

Soluble  Starch. — Starch  is  manufactured  in  several 
grades  with  regard  to  thickening  quality.  With  long 

1  Maquenne  and  Roux:  Ann.  Chim.  Pkys.,  1906  [8],  9,  179. 
Matthews  and  Lott:/.  Inst.  Brewing,  1911,  17,  219-266. 


110  HOUSEHOLD    CHEMISTRY 

continued  heating  or  heating  under  pressure  at  130°- 150°, 
with  ten  times  its  weight  of  water,  a  form  of  starch  is 
prepared  which  goes  into  true  solution.  It  does  not 
gelatinize,  but  gives  the  iodine  reaction  and  does  not 
reduce  Fehling's. 

Reaction  with  Iodine. — This  is  the  most  characteristic 
test  for  starch.  A  deep  blue  color  is  produced  whether 
the  granule  is  ruptured  or  not.  The  compound  formed 
is  called  starch  iodide. 

Action  of  Acids  and  Alkalies. — On  boiling  with  dilute 
(2  per  cent.)  HC1  or  H2SO4,  starch  is  hydrolyzed  to 
dextrins  and  maltose,  and  finally  to  glucose.  Concen- 
trated H2SO4  causes  a  complete  carbonization  of  air-dry 
starch  in  a  short  time.  Strong  HC1  on  dry  starch  causes 
a  swelling  of  the  granules  and  in  a  short  time  a  change 
to  the  soluble  form.  If  the  action  is  continued  for  a 
few  days,  hydrolysis  of  the  granules  to  achroodextrin, 
maltose  and  glucose  results,  while  the  starch  cellulose 
remains  unchanged.  With  nitric  acid  various  products 
are  formed  according  to  conditions.  On  boiling  with 
strong  HNO3  (specific  gravity  1.2)  starch  is  converted 
into  oxalic  acid.  With  cold  concentrated  HNO3  com- 
pounds may  be  formed  similar  to  the  nitrates  of  cellulose. 
In  presence  of  cold  strong  fixed  alkali,  starch  is  solu- 
ble with  partial  hydrolysis  and  usually  the  product  has 
a  distinct  yellow  color;  weaker  solutions  have  very  little 
effect  unless  heated. 

Action  of  Enzymes. — Amylases,  whether  the  diastase  of 
grains,  the  ptyalin  of  the  saliva,  or  the  amylopsin  of 


HOUSEHOLD    CHEMISTRY  III 

the  pancreatic  secretion,  hydrolyze  starch  to  maltose. 
The  first  reaction  is  a  quick  change  of  starch  paste  to 
soluble  starch.  Shortly  after,  the  blue  color  with  iodine 
gives  place  to  a  reddish  brown,  showing  the  presence 
of  erythrodextrin.  At  the  same  time  maltose  is  formed. 
The  change  may  be  expressed  as : 

(C6H1005)n  +  HOH  ~  C12H220H  +  (C6H1005U- 

maltose  dextrin 

As  the  action  continues  an  achroodextrin  stage  is  reached 
where  the  iodine  ceases  to  act,  and  the  amount  of  re- 
ducing sugar  is  increased.  According  to  Maquenne  and 
Roux,  the  maltose  is  produced  from  the  principal  con- 
stituent of  the  granule,  amylose,  and  the  residual  dextrin 
comes  from  the  amylo-pectin,  which  is  slowly  changed 
by  enzyme  action,  but  does  not  yield  a  reducing  sugar. 
Experiments  by  these  investigators  and  others  show 
about  80  per  cent,  of  maltose  formed  after  2  hours  of 
diastatic  action.  Hydrolysis  with  diastase  proceeds  most 
rapidly  at  a  temperature  of  about  55°. 

Fermentation. — Various  organisms  are  known  which 
ferment  starch  to  alcohol.  With  yeast  there  is  no  direct 
fermentation;  if  a  diastatic  enzyme  is  present  in  the 
starch  hydrolysis  to  maltose  may  take  place,  in  which  case 
the  maltase  in  ordinary  yeast  carries  the  hydrolysis  to 
glucose.  This  in  turn  is  converted  by  zymase  to  various 
substances,  chiefly  carbon  dioxide  and  alcohol. 

EXPERIMENTS  ON  STARCH. 

.  i.  Occurrence  of  Starch — Examine  a  thin  section  of  potato 
under  the  microscope.  Make  a  careful  drawing  of  the  structure 
of  the  cells  and  the  granules  within.  Cover  the  section  with  a 


112  HOUSEHOLD    CHEMISTRY 

thin  glass  and  introduce  a  minute  trace  of  iodine  solution  at  the 
edge  of  the  cover  glass.  Note  and  make  a  colored  (blue  pencil) 
diagram  of  the  result. 

2.  Extraction  of  Starch — Clean  and  peel  one  end  of  a  small 
potato,  rub  it  on  an  ordinary  grater,  collect  the  gratings  in  a 
beaker  of  cold  water,  strain,  allow  the  cloudy  liquid  to  stand 
until  starch  settles.    Pour  off  liquid  and  use  the  sediment  for 
following  tests : 

3.  Effect  of  Dry  Heat — Gently  heat  half  an  inch  of  dry  starch 
in  a  clean,  dry  test-tube.    Observe  and  explain  condensed  moist- 
ure in  the  cooler  part  of  the  tube.     Increase  the  heat  somewhat 
and  note  the  odor  of  the  evolved  vapor  and  the  color  of  the 
starch :   What  does  it  suggest  ?    Now  heat  strongly  until  only  a 
black  residue  remains.    What  is  it? 

4.  Effect  of  Strong  Acid. — To  a  small  portion  of  dry  starch 
in  a  porcelain  evaporating  dish  add  a  few  drops  of  concentrated 
sulphuric  acid;  note  the  result  and  after  a  short  time  heat  gently 
and  observe  again. 

5.  Solubility — Treat  a  small  portion  of  finely  pulverized  dry 
starch  with  cold  water,  filter  a  portion  and  examine  the  filtrate 
for  dissolved  material,  by  evaporating  a  little  on  platinum  foil, 
also  by  the  iodine  test. 

6.  Starch  Paste. — Boil  the  remainder  of  the  starch  and  water 
mixture.    Filter    some   of   the   gelatinized    product   and   test   a 
portion  of  the  filtrate  with  iodine.    Explain. 

7.  Conditions   for  Iodine   Tests — To   another   portion   of    the 
cooled  filtrate  add  iodine  solution,  gently  heat  and  allow  to  cool. 
Note  the  result.     Now  boil  for  some  time  and  cool;  the  color 
will  not  return.    Why? 

To  some  starch  solution  in  a  test  tube  add  a  small  portion  of 
caustic  soda  and  a  few  drops  of  iodine  solution  and  note  the 
result.  Repeat  the  experiment  using  dilute  sulphuric  acid  instead 
of  NaOH. 


HOUSEHOLD    CHEMISTRY  113 

8.  Effect  of  Tannic  Acid — Add  a  solution  of  tannic  acid  to 
some  starch  solution.    Note  the  result,  also  any  change  effected 
by  heating. 

9.  Starch  a  Colloidal  Substance — Partly  fill  a  diffusion  thimble 
with  thin  starch  paste,  then  stand  it  in  a  beaker  of  cold  water. 
After  standing  for  some  time,  test  the  water  for  starch  with 
iodine. 

10.  Acid  Hydrolysis. — i. — Make  a  very  weak  solution  of  starch 
in  about  4  ounces  of  boiling  water;  to  this  solution  add  2  cc. 
of  strong  hydrochloric  acid  and  boil  until  clear,  using  a  reflux 
condenser.     At  this  point,  a  small  quantity  of  the  cooled  liquid 
should  give  no  blue  coloration  with  iodine  solution.    If  this  is 
not  the  case  add   10  drops   of   the  same  acid   and   boil    some 
minutes  longer,  or  until  a  small  portion  gives  no  test  with  iodine 
as   above.    Now   neutralize   the   remainder   of   the   liquid   with 
sodium  carbonate  solution,  add  i  or  2  cc.  to  Fehling's  solution 
and  boil.    If   reduction  does  not  take  place  add  more  of  the 
solution  and  boil  again. 

2.  Mix  about  I  gram  of  starch  with  10  cc.  of  strong  HC1  and 
allow  the  mixture  to  stand  for  15  minutes.  Now  pour  off  a 
small  portion  and  add  an  excess  of  cold  water.  A  milky  pre- 
cipitate of  soluble  starch  results.  Filter  this  and  test  its  solu- 
bility in  hot  water.  Allow  the  remainder  of  the  acid  mixture 
to  stand  for  several  days,  until  the  viscous  mass  becomes  clear 
and  separates  into  2  layers.  The  upper  layer  contains  starch 
cellulose.  Remove  and  test  with  iodine.  Neutralize  the  lower 
layer  and  make  the  Fehling's  test. 

Enzyme  Hydrolysis — i.— Take  about  25  cc.  of  clear  dilute 
starch  paste  in  a  small  beaker  and  add  2  or  3  cc.  of  undiluted 
saliva  which  has  been  filtered  through  coarse  filter  paper. 

Keep  at  body  temperature  and  from  time  to  time  pour  off 
small  portions  and  test  with  iodine  solution,  keeping  each  for 
comparison.  Note  the  gradual  change  from  blue  to  red  to 
yellow  and  finally  to  colorless.  When  this  stage  is  reached,  add 
a  small  portion  of  the  material  to  Fehling's  solution,  boil,  and 
note  reduction  due  to  maltose. 


114  HOUSEHOLD    CHEMISTRY 

2.  To  25  cc.  of  dilute  starch  paste  add  about  5  cc.  of  diastase 
solution  and  keep  at  55°.  Test  portions  from  time  to  time  with 
iodine  until  the  test  fails  to  give  a  color  (maltose).  At  this  stage 
boil  the  remainder  of  the  solution  with  about  25  drops  of  dilute 
sulphuric  acid  for  10  minutes.  Neutralize  and  test  this  with 
Fehling's  solution  for  glucose. 

Dextrin. 

The  dextrins  are  colloidal  compounds,  soluble  in  water, 
and  precipitated  by  strong  alcohol.  As  starch  hydrolysis 
proceeds  a  number  of  dextrins  are  formed :  the  dextrin 
which  gives  a  red-brown  color  with  iodine  is  termed 
erythrodextrin ;  that  which  is  forming  as  iodine  ceases  to 
act  is  achroodextrin.  A  maltodextrin  is  known  to  which 
the  formula  6(C6H10O5)H2O  has  been  assigned.  It  ap- 
pears to  be  a  chemical  combination  of  one  part  maltose 
and  two  parts  dextrin,  and  is  a  reducing  substance.  Dex- 
trins proper  are  not  considered  to  have  reducing  power 
when  pure. 

Dextrins  are  used  to  a  great  extent  in  textile  and 
other  industries  for  sizings,  as  a  medium  for  colors  in 
textile  printing,  as  gum,  paste,  etc.  They  also  form  about 
half  the  carbohydrate  material  in  corn  syrup. 

Preparation. — Dextrin  or  "British  Gum"  is  prepared 
commercially  by  two  methods :  ( i )  Dry  starch  is  heated 
to  2OO°-25O°  over  an  oil  bath,  in  a  steam  jacket,  or  other 
device  to  insure  the  requisite  temperature  without  char- 
ring. The  product  is  dark  in  color,  but  has  good  adhesive 
quality.  (2)  The  starch  is  moistened  with  nitric  or  hy- 
drochloric acid,  dried,  and  heated  to  140°- 170°.  The 
result  of  this  partial  hydrolysis  is  a  light  colored  dextrin 


HOUSEHOLD    CHEMISTRY  1 15 

containing  some  sugar,  and  having,  therefore,  less  ad- 
hesive power.  Dextrin  may  be  prepared  more  con- 
veniently by  heating  a  strong  starch  paste  with  moder- 
ately dilute  sulphuric  acid  until  clear,  cooling  and  pre- 
cipitating by  adding  to  ethyl  alcohol. 

EXPERIMENTS  ON  DEXTRIN. 

Solubility — Compare  the  solubility  of  dextrin  in  cold  water 
and  in  boiling  water. 

To  successive  portions  of  cooled  dextrin  solution  in  test  tubes 
add: 

1.  Alcohol  up  to  60  per  cent,  by  volume. 

2.  Iodine  solution. 

3.  Caustic  soda  and  iodine  solutions. 

4.  Sulphuric  acid  and  iodine  solutions. 

5.  A  few  drops  of  ammonia  and  basic  acetate  of  lead;  note 
the  result. 

6.  To   boiling   Fehling's   solution :    if   pure   there   will   be   no 
reaction. 

7.  Tannic  acid  as  under  starch. 

8.  For   the   hydrolysis   of    dextrin   by   enzyme    action,    follow 
the  method  given  under  starch. 

Grlycogen. 

Glycogen  is  known  as  animal  starch,  since  it  appears 
as  the  reserve  carbohydrate  in  the  developing  cells  of 
animal  organisms.  It  is  present  in  the  liver  in  consider- 
able quantity ;  to  a  less  extent  in  blood,  muscle  and  several 
glands.  Its  formula  is  (C6H10O5)  n.  In  appearance 
glycogen  is  a  white,  amorphous  powder.  It  is  soluble 
to  opalescence  in  water,  insoluble  in  strong  alcohol,  and 
hydrolyzes  as  starch  does  with  diastase  or  with  acids. 
It  gives  a  brownish  red  color  with  iodine,  does  not  re- 


Il6  HOUSEHOLD   CHEMISTRY 

duce  Fehling's,  and  is  not  fermentable  by  yeast.  It  may 
be  extracted  in  considerable  quantity  from  the  large 
muscle  of  the  scallop,  as  directed  below: 

Preparation. — Grind  a  mixture  of  scallops  and  sand  in 
a  mortar,  transfer  to  a  beaker,  add  enough  water  to 
cover  the  mass  and  boil.  This  dissolves  the  glycogen 
and  partially  precipitates  the  proteins,  which  are  now 
completely  precipitated  by  partially  cooling  and  adding 
a  few  drops  of  acetic  acid.  Filter  and  add  the  filtrate  to 
alcohol  (95  per  cent.).  Glycogen  will  come  down  as  a 
white  precipitate.  Allow  to  settle,  decant  the  clear 
liquid,  and  filter  the  residue. 

Apply  the  following  tests  to  the  glycogen  thus  ob- 
tained : 

1.  Solubility  in  water;  look  for  opalescence. 

2.  Solubility  in  10  per  cent,  sodium  chloride  solution. 

3.  Solubility  in  hydrochloric  acid. 

4.  Solubility  in  caustic  potash. 

5.  Reaction  with  iodine  solution. 

6.  Boil  a  dilute  solution  of  glycogen  in  a  beaker  for  15  minutes 
with  2  cc.  of  dilute  hydrochloric  acid,  neutralize  with  sodium 
carbonate  and  test  with  Fehling's  solution.    What  change  has 
taken  place? 

Celluloses. 

These  compounds,  represented  by  the  general  formula 
ttC«H10O5,  are  at  once  the  most  complicated  and  stable 
of  the  carbohydrates. 

They  may  be  roughly  divided  into  the  simple  and 
compound  celluloses,  the  former  unicellular  in  structure 
and  the  latter  multicellular. 

Cotton,  thistledown,  and  the  internal  fibrous  network 


HOUSEHOLD   CHEMISTRY  1 1/ 

of  grains  and  vegetables  are  simple  celluloses  and  occur 
as  ribbon-like  bands  with  curled  edges  and  a  characteristic 
corkscrew  twist.  These  forms  contain  little  protein,  gum, 
fat  or  mineral  matter.  Flax,  grasses  and  woody  fiber  are 
compound  celluloses,  occurring  for  the  most  part  as 
jointed  rods  or  tubes,  and  are  highly  charged  with  pro- 
tein, fat,  gum  and  mineral  matter.  Cotton  is  the  only 
unicellular  form  of  cellulose  of  industrial  import- 
ance, while  the  multicellular  type  has  many  representa- 
tives, i.  e.,  linen,  hemp,  jute,  ramie  and  a  great  variety 
of  woods. 

The  treatment  of  cotton  does  not  involve  any  exten- 
sive chemical  operations,  but  is  chiefly  confined  to 
mechanical  manipulation.  The  compound  celluloses  on 
the  other  hand  require  complex  and  prolonged  chemical 
or  bacterial  treatment  before  the  fiber  is  ready  for  the 
operations  of  spinning,  weaving  and  dyeing.  Woody 
fiber  is  now  generally  used  for  the  preparation  of  the 
felted  fabric  known  as  paper.  It  is  necessary  an  this  case 
to  remove  all  impurities  by  chemical  means,  and  to  break 
up  the  long  fibers  by  grinding  before  the  fabric  can  be 
prepared. 

General  Properties  of  the  Celluloses. — Celluloses  are 
insoluble  in  water  hot  or  cold,  and  in  weak  acids  or 
alkalies.  Strong  acids  and  alkalies  cause  them  to  hydro- 
lyze;  in  some  cases  soluble  forms  result  by  heating  or 
prolonged  action  in  the  cold,  or  by  a  combination  of  both 
methods.  Generally  speaking,  the  action  of  acids  is  more 
rapid.  When  partially  hydrolyzed  they  are  colored  blue 


Il8  HOUSEHOLD   CHEMISTRY 

in  the  presence  of  iodine.  Nitric  acid  in  concentrated 
form  converts  cellulose  into  nitric  compounds  of  varying 
composition,  containing  one  to  six  nitrate  groups;  the 
form  depending  on  the  duration  of  the  nitrating  process. 
All  of  these  compounds  are  very  unstable  and  dissociate 
into  water,  carbon  dioxide  and  nitrogen,  when  slightly 
heated ;  hence  their  use  as  explosives.  Cellulose  nitrates, 
unlike  cellulose,  dissolve  in  ether,  alcohol  or  acetone  or 
mixtures  of  these  solvents  (collodion)  and  on  evapora- 
tion yield  transparent  structureless  films,  used  in  medi- 
cine, photography  and  for  the  preparation  of  artificial 
silk.  Ammoniacal  cupric  oxide  (Schweitzer's  Reagent) 
and  concentrated  zinc  chloride  dissolve  simple  cellulose 
on  gentle  warming.  Hydrocellulose  precipitates  from 
these  solutions  on  acidifying  with  acetic  acid. 

Lignocellulose  (wood)  yields  oxalic  acid  on  treatment 
with  nitric  acid,  and  oxalate  of  potash  on  fusion  with 
caustic  potash. 

Cellulose  fibers  are  characterized  by  high  capillary 
capacity  and  heat  conductivity ;  hence  their  use  for  lamp 
wicks,  toweling  and  summer  clothing.  These  properties, 
however,  may  be  much  modified  by  tight  twisting  and 
close  weaving,  as  in  the  case  of  canvas. 

While  ordinary  cellulose  is  considered  an  anhydride  of 
glucose,  and  hydrolyzes  to  glucose,  a  hemi-cellulose  is 
known  which  yields  mannose,  galactose,  arabinose  and 
xylose  on  hydrolysis,  but  no  glucose. 

EXPERIMENTS  ON  CELLULOSE. 

(a)  Effect  of  Heat  (Charring) — Heat  a  piece  of  fibrous  ma- 
terial in  a  clean  dry  test-tube.  Note  the  odor  of  the  gases 


HOUSEHOLD   CHEMISTRY  119 

evolved  and  test  the  vapor  with  blue  litmus  paper.  Examine  the 
charred  mass  with  a  .magnifier. 

(&)  Solubility  in  Water — Try  to  dissolve  some  fibrous  ma- 
terial in  water. 

(c)  Solubility  in  Zinc  Chloride — Dissolve  some  absorbent  cot- 
ton in  acid  zinc  chloride  solution,  (ZnCl2  dissolved  in  twice  its 
weight  of  concentrated  HC1).  Precipitate  by  dilution  and  com- 
pare the  result  with  the  original  substance. 

(rf)  Solubility  in  Schweitzer's  Reagent. — Dissolve  some  absorb- 
ent cotton  in  Schweitzer's  reagent,  add  the  resulting  solution  to 
95  per  cent,  alcohol  and  compare  the  precipitate  with  the  original 
substance. 

(e)  Structure — Examine  carefully  the  structure  of  cotton  and 
linen  fibers  under  a  microscope. 

(/)  Crude  Fiber. — Crude  cellulose  of  wood,  grains,  etc.,  is  de- 
termined as  follows : 

Take  I  gram  of  the  dried,  ground  sample,  boil  with  100  cc. 
of  1*4  per  cent,  sulphuric  acid,  when  cool  strain  through  muslin. 
Wash  once  with  hot  water.  Scrape  the  residue  from  the  muslin 
and  boil  it  with  100  cc.  of  iJ4  per  cent,  caustic  soda.  Strain 
again  through  the  same  piece  of  muslin,  wash  with  hot  water, 
then  with  alcohol,  and  finally  with  ether.  Weigh  the  dried 
residue. 

Nitrating — Treat  a  piece  of  filter  paper  or  some  absorbent 
cotton  with  a  cooled  mixture  of  20  cc.  concentrated  HsSO*  and 
10  cc.  concentrated  HNO3.  Keep  the  solution  cool.  Several 
nitrates  of  cellulose  may  form.  The  hexa-  and  penta-nitrates  are 
the  most  prominent.  The  hexa-nitrate  of  cellulose  is  called  gun 
cotton.  Wash  the  product  in  water  and  dry.  Test  its  inflam- 
mability, and  its  solubility  in  a  mixture  of  40  per  cent,  alcohol 
and  60  per  cent,  ether.  The  clear  solution  is  collodion.  Observe 
how  a  film  of  it  hardens  in  the  air.  When  pressed  through 
capillary  tubes,  filaments  are  produced,  which  are  denitrated  and 
further  treated  to  form  one  class  of  artificial  silk — the  nitra- 
cellulose  or  pyroxylin. 


I2O  HOUSEHOLD   CHEMISTRY 

Mercerization — Stretch  some  cheesecloth  or  muslin  tightly  over 
a  porcelain  dish  and  immerse  for  15  minutes  in  a  25  per  cent, 
solution  of  caustic  soda,  at  a  temperature  of  about  20°.  An 
alkali-cellulose  forms,  and  the  cloth  appears  semi-transparent. 
Wash  free  from  alkali,  dry,  and  notice  the  appearance  of  the 
mercerized  cotton  compared  with  the  original  material.  Try 
its  reaction  with  iodine.  The  cotton  has  become  cellulose  hy- 
drate, n(C,H10O5)H,O. 

Methods  of  Distinguishing  Cotton  from  Linen. — The 
microscope  is  the  one  reliable  means  of  differentiating 
these  fibers,  since  full-bleached  linen  and  cotton  are 
practically  identical  in  chemical  composition.  How- 
ever, the  following  tests  are  helpful  if  a  microscope  is 
not  available: 

Breaking  and  Burning  Tests. — Unraveled  threads  of  linen 
fabrics  are  untwisted  and  broken  by  holding  between  the  thumbs 
and  index  fingers  and  pulling  apart  slowly  and  steadily.  Linen 
parts  slowly,  and  with  pointed  ends ;  cotton  breaks  suddenly 
with  tasselled  ends.  Burn  a  small  tuft  of  each  fiber  and  note 
the  condition  of  the  fiber  ends. 

Sulphuric  Acid  Test. — Place  a  piece  of  union  toweling  in  con- 
centrated HaSO4  for  about  il/2  minutes.  Remove,  wash,  and  note 
the  comparative  strength  of  the  cotton  and  linen  threads.  Cotton 
will  be  destroyed  in  2  minutes  or  less;  linen  as  a  rule  not  so 
quickly. 

TESTS  ON  LIGNOCELLULOSE. 

(a)  Structure.— Examine  carefully  the  character  of  the  fibers, 
e.  g.t  hemp  or  jute. 

(£)  Phloroglucinol  Test.— Phloroglucinol,  in  HC1,  gives  a  deep 
magenta  coloration  with  any  of  the  lignocelluloses. 

The  reagent  is  prepared  by  dissolving  the  phenol  to  saturation 
in  HC1  ( i  .06  specific  gravity ) . 

(c)  Saturate  moist  jute  fiber,  held  in  a  glass  tube,  •with  chlorine 
gas  and  then  pass  SO,  through  it.  Note  the  characteristic  reaction, 
a  deep  magenta  color. 


HOUSEHOLD   CHEMISTRY  121 

TESTS  ON  PAPER. 

Determine  starch  as  filler  with  iodine  solution.  Determine 
"size"  by  moistening  the  paper  with  Millon's  reagent  and  warm- 
ing gently. 

Parchment  Paper. — Dip  starch-free  paper  in  a  cold  mixture  of 
water  and  H2SO4(2:3),  withdraw  quickly,  wash  in  clear  water 
and  dry.  Compare  with  an  untreated  sample.  Make  the  iodine 
test.  (Cellulose  in  the  presence  of  certain  dehydrating  agents 
responds  to  iodine. ) 

Practical  Work  on  Carbohydrates. 

I.  EXAMINATION  OF  CEREALS. 

Materials. — Ready-to-eat  cereals  of  different  types — flaked, 
and  shredded.  Uncooked  cereals — rolled  and  granular. 

Method:  i.  Grind  samples  fine  in  mortar.  Make  cold  water 
solution.  Filter.  Examine  filtrate  as  follows : 

a.  For  soluble  starch  (iodine). 

b.  For   dextrin.    Add  carefully   to  95   per   cent,  alcohol. 

Note  precipitate.  Continue  adding  the  filtrate,  observ- 
ing whether  the  precipitate  decreases  in  amount.  If 
so,  the  alcohol  has  been  diluted  below  60  per  cent., 
and  dextrin  has  gone  into  solution.  Starch  remains 
insoluble.  If  much  dextrin  is  present  iodine  will  show 
it. 

c.  For    reducing    sugar.    Make    Fehling's    and    Barfoed's 

tests. 

d.  For  protein.    Make  biuret  test  (see  p.  148). 

2.  Stain  a  portion   of  the   residue  with   iodine  and   examine 
under  the  microscope  for  unbroken  starch  granules. 

3.  In  a  muffle  furnace,  burn  to  ash  about  5  grams  of  oats, 
rice,  etc.    Take  up  the  ash  with  boiling  water  and  a  few  drops 
of  HNOs.    Filter,  cool  and  test  for  Fe,  Ca,  Mg,  K,  Na,  P  and  Cl. 

II.  COOKING  of  CEREALS. 

Cook  different  cereals  for  the  minimum  time  stated  on  the 
package.  Observe  condition  of  granules  under  microscope. 


122  HOUSEHOLD    CHEMISTRY 

(Note  that  a  ruptured  granule  does  not  always  lose  its  form  or 
contents.)     Observe  again  after  a  longer  cooking. 

III.  PREPARED  SOUPS. 
Treat  prepared  dried  puree  soups  as  in  II  and  observe. 

IV.  CRACKERS,  BREAD,  TOAST,  ETC. 

Examine  as  in  I  for  unchanged  and  changed  starch,  dextrin 
and  reducing  sugar.  Compare  under  microscope  stained  slides 
of  bread  from  crust  and  center  of  loaf. 

V.  POTATOES. 

Bake  and  boil  until  cooked.  Examine  under  microscope. 
Make  salivary  digestion  test  on  well-cooked  potato,  examining 
under  the  microscope  the  condition  of  the  granules  in  the  dextrin 
and  maltose  stages. 

VI.  HYDROLYTIC  CHANGES. 

Test  sugars  for  reducing  action  after  boiling  with  cream  of 
tartar  (fondant  making),  lemon  juice,  or  other  acid  fruit  juice. 
Note  time  required  for  hydrolysis  and  the  completeness  of  the 
change.  Make  similar  tests  on  starch  and  compare  with  sugar 
as  to  quickness  of  action. 

VII.  HONEY  AND  SYRUPS. 
Test  for  cane  and  invert  sugars. 

VIII.  THICKENING   POWER. 

Note  comparative  thickening  power  of  potato,  corn,  and  wheat 
starches,  and  time  required  for  cooking. 

Preparation  of  Gluten. — Take  25  grams  of  white  bread, 
macaroni  or  whole  wheat  flours,  mix  on  a  porcelain  or 
glass  plate  with  the  least  amount  of  water  to  make  a  stiff 
dough  (12-15  CC0-  Do  not  handle  the  dough  with  the 
fingers,  use  a  flexible  steel  knife.  Transfer  the  dough  to 
a  well-washed  piece  of  muslin,  taking  care  to  clean  the 


HOUSEHOLD    CHEMISTRY  123 

mixing  surface  and  knife  thoroughly;  tie  up  the  muslin 
in  the  form  of  a  bag  and  wash  under  a  gentle  stream  of 
water,  manipulating  well  with  the  fingers.  Continue  the 
washing  until  the  liquid  runs  clear  from  the  bag,  and 
fails  to  give  the  test  for  starch  with  iodine.  Be  careful 
to  collect  all  the  washings  in  a  tall  glass  beaker  or  jar — 
(they  should  amount  to  from  I  to  il/2  liters).  Strain 
through  muslin  and  stand  the  filtrate  aside  in  a  cool 
place  for  settling.  Reserve  for  future  use.  Examine 
the  residue  with  a  lens.  Squeeze  out  as  much  water  as 
possible  from  the  bag,  untie  it  and  collect  and  weigh  the 
moist  gluten ;  spread  it  out  in  a  thin  cake  and  dry  it  for 
i  hour  at  ioo°-io5°.  Cool  and  weigh  the  dry  gluten. 
When  the  contents  of  the  jar  have  settled,  decant  the 
clear  liquid,  and  test  small  portions  of  it  for  protein  with 
the  biuret  test  and  for  soluble  carbohydrate  with  Feh- 
ling's  reagent. 

Pour  distilled  water  on  the  residue  in  the  jar  and  stir 
up  the  mixture,  allow  it  to  settle  and  decant  as  before. 
Repeat  this  operation  twice,  and  then  collect  the  residue 
on  balanced  filter  papers ;  dry  and  weigh.  This  last 
weight  gives  the  starch  and  fiber  content,  but  in  the  case 
of  ordinary  wheat  flours  the  latter  is  so  small  that  it  may 
be  neglected. 

NOTE. — In  the  case  of  a  whole  wheat  flour  it  is  best  to  pass  the 
sample  through  a  loo-mesh  sieve,  taking  the  screenings  for  the 
determination  of  starch,  gluten,  etc. 


CHAPTER  VIII. 


FRUITS  AND  FRUIT  JUICES. 

Composition. — Analyses  of  fresh  fruits  show  similar- 
ities in  composition,  so  that  a  general  description  is  suf- 
ficient. The  percentage  of  water  is  always  high,  being 
from  75  per  cent,  to  more  than  90  per  cent,  in  the  edible 
portion.*  The  next  highest  constituent  is  the  carbohy- 
drate bodies. 

The  carbohydrates  in  ripe  fruits  are  principally  glu- 
cose and  fructose.  Starch  and  acids  decrease  as  fruit 
ripens;  invert  increases.  Sucrose  normally  disappears 
with  the  increase  of  invert.  Many  fruits,  especially 
berries,  contain  little  or  no  sucrose;  in  apples,  pears, 
peaches,  apricots,  oranges,  plums  and  pineapple  the 
amount  is  comparatively  high.  Celluloses,  forming  the 
fiber  content,  are  of  course  a  considerable  carbohydrate 
part  of  some  fruits.  Pectose  is  found  combined  as 
pectocellulose  in  the  lamellae  of  cell  walls.  When  hy- 
drolyzed  with  dilute  acids  or  alkalies,  or  by  pectase,  an 
enzyme  present  in  ripening  fruit,  pectose  changes  to 
pectin.  The  former  is  insoluble  in  water,  and  may  be 
decomposed  into  a  number  of  substances  known  as 
pectinic  acids,  usually  found  combined  with  calcium. 
The  term  pectinase  is  applied  to  the  enzyme  which  coag- 

*  Fruits  and  Fruit  Products,  Bull.  66,  U.  S.  Dept.  Agric.,  Div. 
of  Chem. 

Bull.  28,  Atwater  and  Bryant,  Idem. 


HOUSEHOLD   CHEMISTRY  125 

ulates  the  juices  containing  the  dissolved  pectinous  sub- 
stances, forming  the  so-called  fruit  jellies.* 

This  reaction  is  conditioned  on  the  presence  of  lime, 
and  the  establishment  of  a  certain  equilibrium  between 
the  enzyme  and  the  concentration  of  the  fruit  acid  and 
the  calcium  salts.  Fleshy  roots  and  fruits — carrots,  tur- 
nips, apples  and  pears — are  especially  rich  in  pectocellu- 
loses,  but  many  other  fruits,  e.  g.,  currants,  possess  con- 
siderable amounts. 

In  unripe  fruits  there  is  often  much  tannin,  which  dis- 
appears as  the  fruit  ripens. 

Acidity. — The  acidity  of  most  fruits  is  due  to  mix- 
tures of  organic  acids  and  acid  salts,  such  as  acid  potas- 
sium tartrate.  Citric,  malic  and  tartaric  acids  are  often 
present,  and  may  be  determined  separately.  However, 
for  convenience,  analysts  usually  express  total  acidity  as 
sulphuric  acid. 

Ash  Constituents. — In  most  cases,  these  show  a 
maiked  alkalinity,  and  consist  largely  of  carbonates  of 
sodium,  potassium,  calcium,  and  magnesium.  Sulphates 
and  chlorides  are  found  only  in  traces. 

Proteins. — The  protein  content  is  inconsiderable,  sel- 
dom reaching  more  than  i  per  cent,  in  fresh  fruit.  Much 
of  this  is  insoluble,  and  appears  only  in  small  quantities 
in  the  expressed  juice.  As  a  rule,  the  presence  of  more 
than  i  per  cent,  of  protein  in  a  jelly  would  indicate  that 
gelatin  had  been  used  to  aid  in  the  gelatinizing  of  the 
article. 

*  Kraemer:    Applied  and  Economic  Botany. 


126 


HOUSEHOLD   CHEMISTRY 


The  following  table  from  the  Ann.  de  Chimie  et  de 
Phys.,  Vol.  61,  gives  comparative  figures  as  to  content 
of  reducing  sugar,  sucrose,  total  sugar  and  acid  in 
various  fruits: 


Per  cent, 
of 
reducing 
sugar 

Per  cent, 
of 
sucrose 

Per  cent, 
of 
total 
sugar1 

Per  cent, 
of  acid 
figured  as 
tartaric2 

17.26 
16.50 
12.63 
11-55 

10.00 

9.42 
8.72 

8.42 

8.25 
7.16 
6.40 
5-86 
5-82 
5-45 
5.22 

4.98 
4-36 
4-33 
3-43 
2-74 
1.98 
i.  60 
1.07 
1.  06 

o.oo 
o.oo 
3.20 

0.00 
0.00 

o.oo 

5.28 

0.36 

o.oo 
0.68 
o.oo 
o.oo 

0.43 

2.19 

2.01 

6-33 
4.22 

1.25 
5-24 
1.04 

11-33 
o.oo 
0.92 
0.41 

18.37 
16.50 

15.83 
H-55 

I  O.OO 

9-42 
13.40 
8.78 

8.25 
7.84 
6.40 
5-86 
6.25 
7.64 
7-23 

11.31 

8.58 

5-55 
8.67 

3-78 
13-30 
i.  60 
1.99 
1.47 

0-345 
0.403 
0.403 
0.057 
0.661 
0.558 
1.148 
0.115 
0.608 
0.287 

1-574 
0.750 
0-253 
0-633 
1-580 

0-550 
0.448 
1.208 
1.288 
1.864 

0-547 
2.485 

0.783 
4.706 

Violet  fitrs  

White  heart  cherries  

Strawberries  (different 

Queen  Claude  plums  .... 

1  Quoted  by  Buegnet. 

2  Quoted  by  Konig. 

ANALYSIS  OF  A  FRUIT.* 

Water  and  Total  Solids — Weigh  out  about  20  grams  of  the 
*  Bull.  66,  Div.  of  Chem,  U.  S.  Dept.  of  Agric. 


HOUSEHOLD   CHEMISTRY  I2/ 

pulped  fresh  fruit,  or  about  as  much  dried  fruit  as  will  give 
3  or  4  grams  of  dried  residue,  place  in  a  weighed  flat  dish,  mix 
with  a  weighed  quantity  (4-5  grams)  of  freshly  ignited  asbestos, 
add  a  few  cc.  of  water,  mix  thoroughly  and  dry  at  100°  for 
20  to  24  hours.  Estimate  water  and  total  solids. 

Determination  of  Ash — Thoroughly  char  the  above  residue  in 
a  platinum  dish  at  as  low  a  heat  as  possible,  extract  with  water, 
filter,  and  wash.  Return  filter  paper  and  insoluble  material  to 
the  dish  and  thoroughly  ignite;  add  the  soluble  portion  and  a 
few  cc.  of  ammonium  carbonate  solution,  and  evaporate  the 
whole  to  dryness.  Now  heat  to  very  low  redness,  cool  in  a 
desiccator,  and  weigh  rapidly.  The  result  is  total  ash  constituents. 

Determination  of  Alkalinity — Run  an  excess  of  N/5  HNO« 
into  the  platinum  dish  containing  the  ash.  Add  a  drop  or  two 
of  methyl  orange.  Mix  carefully  with  a  rubber  tipped  stirring 
rod,  and  titrate  excess  of  acid  with  N/io  KOH.  Calculate 
alkalinity  as  potassium  carbonate. 

Total  Adds. — Dilute  10  grams  of  fruit  juice  or  pulped  fruit 
up  to  250  cc.,  with  recently  boiled  distilled  water.  In  the  case  of 
fruit  pulp  boil  for  a  minute  or  two,  to  dissolve  all  acid  from  the 
fruit  cells.  Add  phenolphthalein  and  titrate  against  N/io  KOH. 
Calculate  as  H2SO4. 

Scheme  for  the  Separation  and  Identification  of  Malates, 
Citrates,  Tartrates,  Oxalates  and  Acetates. — To  the  filtered  fruit 
juice,  prepared  as  in  the  preceding  experiment,  add  Ca(OH)2, 
preferably  in  the  form  of  milk  of  lime,  until  the  neutral  point 
is  reached.  Avoid  excess.  (If  the  fruit  juice  is  neutral  at  the 
start  add  CaCU  solution  as  long  as  a  precipitate  forms.)  Stir 
well,  filter  and  wash.  Proceed  as  follows  with  (i)  residue; 
(2)  filtrate: 

i.  Residue.  (Containing  calcium  tartrate  and  oxalate). — 
Treat  on  a  filter  with  acetic  acid.  Residue  is  calcium  oxalate, 
soluble  in  hydrochloric  acid.  Filtrate  contains  calcium  acetate 
and  tartaric  acid.  Add  95  per  cent,  alcohol  and  potassium  hy- 
droxide, and  shake  well.  On  standing  acid  potassium  tartrate 
appears  as  well-defined  crystals. 


128  HOUSEHOLD   CHEMISTRY 

2.  Filtrate.  (Containing  calcium  malate,  citrate  and  acetate.) — 
Boil,  filter,  and  wash  with  hot  distilled  water.  Reserve 
filtrate.  Residue  is  calcium  citrate.  Treat  on  filter  with  dilute 
sulphuric  acid.  Residue  is  calcium  sulphate.  To  the  solution 
add  silver  nitrate  and  dilute  ammonia — a  white  precipitate  of 
silver  citrate  forms  which  does  not  blacken  on  boiling.  The  re- 
served filtrate  contains  calcium  malate  and  acetate.  Concentrate, 
cool,  and  add  to  a  large  excess  of  ethyl  alcohol.  Filter  and 
wash.  Residue,  calcium  malate.  Solution,  calcium  acetate.  To 
this  add  sulphuric  acid  and  heat.  Note  odor  of  ethyl  acetate. 

Determination  of  Nitrogen. — Use  5  grams  of  fruit  jelly,  or 
10  grams  of  fresh  juice  or  fruit.  Follow  the  Kjeldahl  method 
described  in  Chapter  XVI.  Use  6.25  as  the  nitrogen  factor. 

Determination  of  Carbohydrates. —  (a)  Reducing  Sugar. — 
Treat  25  grams  of  fruit  juice  or  pulp  with  basic  lead  acetate 
in  excess  (2  to  5  cc.),  make  up  to  100  cc.  and  filter.  Transfer 
from  25  to  50  cc. — depending  upon  the  percentage  of  reducing 
sugar  present — to  a  100  cc.  flask  and  add  a  saturated  solution 
of  sodium  sulphate  in  sufficient  amount  to  precipitate  the  excess 
of  lead;  complete  the  volume  to  100  cc.,  filter,  and  determine 
reducing  sugar  by  Allihn's  method.  (See  Chapter  XVI.) 

(&)  Cane  Sugar. — When  only  a  small  amount  of  cane  sugar 
is  present,  it  is  best  determined  by  calculation  from  the  increase 
in  reducing  sugars  after  inversion.  Treat  double  the  amount 
of  fruit  or  juice  used  in  (a)  with  basic  lead  acetate,  make  up 
to  loo  cc.,  filter,  and  invert  50  cc.  in  a  100  cc.  flask  with  5  cc. 
of  hydrochloric  acid.  (See  Chapter  XVI.)  After  inversion 
nearly  neutralize  the  acid  with  sodium  hydroxide,  precipitate 
the  excess  of  lead  with  sodium  sulphate,  and  dilute  with  water 
to  100  cc.  Filter  and  dilute  so  that  the  solution  does  not  con- 
tain more  than  I  per  cent,  of  reducing  sugar.  The  per  cent, 
of  increase  in  reducing  sugar  after  inversion,  multiplied  by  0.95, 
equals  the  per  cent,  of  cane  sugar. 

Pentoses  and  Pentosans. — Furfural  Test. — Place  25  grams  of 
the  fruit  juice,  diluted  to  100  cc.,  in  an  Erlenmeyer  flask,  add 


HOUSEHOLD   CHEMISTRY  I2Q 

HC1  of  1.06  specific  gravity  and  boil.  Hold  in  the  vapor  a  filter 
paper  moistened  with  a  solution  of  equal  parts  of  anilin  and 
50  per  cent,  acetic  acid.  A  bright  red  color  appears  on  the 
paper  if  more  than  traces  of  furfural  are  present.* 

Dextrin. — A  qualitative  test  may  be  made  by  decolorizing  the 
diluted  fruit  juice  with  boneblack,  and  observing  the  color  reaction 
with  iodine.  Another  method  of  decolorizing  consists  in  bringing 
the  solution  nearly  to  the  boiling  point,  then  adding  several 
cubic  centimeters  of  dilute  (i  to  3)  sulphuric  acid  and  gradually 
potassium  permanganate.  Stir  until  the  color  disappears. 

Alcohol  Precipitate. — If  alcohol  is  added  in  excess  to  a  solu- 
tion of  a  fruit  product,  such  as  a  jelly,  a  flocculent  precipitate 
may  form  with  no  turbidity,  indicating  a  pure  fruit  product.  A 
white  turbidity  appearing  at  once,  followed  by  a  thick,  gummy 
precipitate,  shows  the  presence  of  glucose.  In  fresh  fruit  juices 
there  is  often  marked  turbidity  which  is  caused  by  the  starchy 
matters  present. 

Experiment  in  Jelly-Making. — To  determine  the  optimum  con- 
ditions for  gelatinizing  fruit  juices,  treat  cranberries,  apples,  cur- 
rants, and  other  jelly-making  fruits  as  follows: 

1.  Express  the  juice  from  the  raw  fruit  and  allow  a  portion 
to  stand.    Is  there  gelatinization  in  any  case? 

2.  Bring  another  portion  to  a  boil.    Cool  and  observe. 

3.  Boil   other   portions    for   measured   periods,   increasing   in 
duration.    What  is  the  relation  of  time  to  jelly  formation? 

4.  Repeat  (2)  and  (3),  adding  an  equal  bulk  of  sugar  to  the 
fruit  juice  at  the  boiling  point. 

5.  Repeat  (2),  (3)  and  (4),  modifying  as  follows: 

(a)  Heat  the  fruit  until  -the  skins  burst,  and  express  the  juice. 

(&)  Boil  the  fruit  for  5  minutes  and  express  the  juice. 

Isolation  of  Pectin. — Grate  fresh  white  turnips  and  extract  all 
solubles  with  cool  distilled  water.  Macerate  the  extracted  residue 
with  cold  dilute  HC1  (i:  15)  for  48  hours,  pour  off  the  liquid 
and  precipitate  pectose  bodies  by  adding  an  equal  bulk  of  ethyl 
alcohol. 

*  See  Sherman:    Otganic  Analysis. 


CHAPTER  IX. 


FATS. 

Fats  and  oils  are  widely  distributed  in  vegetable  and 
animal  forms  of  life.  The  line  of  distinction  between. 
a  fat  and  an  oil  is  not  closely  drawn,  but  fats  are  gener- 
ally found  as  solids  at  about  20°  ;  oils  as  fluids.  True 
fats  and  oils  are  esters,  in  which  the  base  is  always 
glycerol,  although  the  fatty  acids  vary.  They  are  there- 
fore glycerides,  the  type  formation  of  which  is  repre- 
sented by  the  equation: 


CSH5(OH)S  +  3  C 

glycerol  stearicacid 

(C17H35COO)3  C3H5  +  3H.O. 

glyceryl  tristearate 
or  stearin 

As  found  in  nature,  fats  are  not  simple  glycerides, 
but  mixtures  of  two  or  more.  For  instance,  from  mut- 
ton and  beef  fat,  a  distearopalmitin,  a  dipalmitostearin 
and  a  dipalmito-olein  have  been  separated.* 

The  principal  fatty  acids  represented  in  these  mixed 
fats  are: 

*  Iveathes:  The  Fats. 


HOUSEHOLD    CHEMISTRY  13! 

Saturated  Acids.  Occurrence. 

Butyric,  CSH,COOH  Chiefly  in  butter. 

Caproic,  C5HUCOOH  In  butter  (1.2%);    in    coconut 

and  palm  oils. 

Caprylic,  C7H15COOH  Same  as  caproic. 

Capric,  C9H19COOH  Same  as  caproic. 

Laurie,  CnH23COOH  Milk  (trace) ;  coconut  and  laurel 

oils. 
Myristic,  Ci3H27COOH  Milk   (trace);  lard,  codliver  oil, 

nutmeg  butter. 
Palmitic,  C15H31COOH  In  most  animal  and  vegetable 

fats,  e.  g.,  palm  oil,   butter, 

lard. 
Stearic,  C17H35COOH  In  most  fats,    especially    solid 

forms. 

Unsaturated  Acids. 

Oleic,  C17H33COOH  In  most  fats  and  oils. 

Linoleic,  CJ7H31COOH  Linseed  oil.     This  or  a  similar 

acid  also  in  other  vegetable 

oils,  including  cotton  seed. 

Since  the  fatty  acids  exist  as  liquids,  semi-solids,  and 
solids,  the  predominating  acid  or  acids  in  a  fat  deter- 
mine its  character  in  this  respect. 

Chemically,  the  glycerides  take  their  name  from  their 
fatty  acid,  combined  with  the  suffix  "in" — thus,  stearin, 
palmitin,  olein,  etc. 

Properties  of  Fats. — Solubilities. — With  few  exceptions, 
fats  are  practically  insoluble  in  cold  water  and  alcohol, 
sparingly  soluble  in  hot  alcohol;  but  dissolve  readily  in 
light  hydrocarbons  such  as  petroleum  ether  and  gasoline. 
All  fats  are  soluble  in  ether,  chloroform,  carbon  tetra- 
chloride  and  benzene. 

Odor  and  Taste. — Pure  neutral  glycerides  are  nearly 


132  HOUSEHOLD   CHEMISTRY 

all  odorless  and  tasteless.  An  exception  is  butyrin, 
found  in  butter,  which  contains  soluble  butyric  acid. 
The  smell  and  taste  of  natural  fats  and  oils  are  due  to 
foreign  substances,  such  as  ethereal  oils. 

Non-volatility. — Fats  and  oils  are  non-volatile,  there- 
fore are  called  fixed,  in  contradistinction  of  ethereal  oils. 
A  result  of  this  property  is  the  formation  of  grease 
spots. 

Crystallinity. — Fats  are  crystalline;  the  crystals  of 
pure  fats  form  a  means  of  identification. 

Melting  and  Solidifying  Points. — In  passing  from  the 
solid  to  the  liquid  state  fats  do  not  alter  in  composition. 
The  melting  and  solidifying  points  of  fats  are  definite 
unless  the  mixture  is  complicated.  The  solidifying  points 
of  oils  range  from  a  few  degrees  above  zero  to  about 
—28°. 

Specific  Gravity. — Most  oils  and  fats  have  a  specific 
gravity  ranging  from  0.910  to  0.975  at  15.5°. 

Effect  of  Heat. — On  prolonged  heating  in  contact 
with  air,  or  heated  above  250°,  fats  and  oils  decom- 
pose, with  formation  of  volatile  products,  notably  acro- 
lein.  Acrolein  is  a  decomposition  product  of  glycerol: 

less  2H2O 

CH2OHCHOH.CH2OH     -~     CH2:  CH.CHO. 

glycerol  acrolein 

It  has  a  peculiar  irritating  odor  characteristic  of  burning 
fat,  and  its  formation  is  a  simple  means  both  of  identi- 
fying the  presence  of  a  fat  and  distinguishing  between 
a  true  fat  or  oil  and  a  hydrocarbon  oil. 


HOUSEHOLD   CHEMISTRY  133 

Emulsification. — This  is  a  physical  change  brought 
about  by  agitating  a  fat  in  the  fluid  state  with  some  emul- 
sifying agent  such  as  egg  albumin  or  soap  solution.  The 
fat  is  broken  up  into  tiny  globules  which  are  coated  with 
the  tenacious  medium  and  thus  prevented  from  coal- 
escing. Emulsions  are  more  or  less  temporary,  as  in  the 
case  of  mayonnaise,  or  the  fat  in  freshly  drawn  milk,  or 
permanent  as  in  certain  commercial  preparations.  Emul- 
sification increases  the  area  for  chemical  action  in  fat 
digestion. 

Drying  Oils. — Three  classes  of  oils  are  recognized: 
Non-drying,  semi-drying,  and  drying.  The  distinctions 
are  made  according  to  their  tendency  to  form  a  dry, 
elastic  film  on  exposure  to  the  air.  The  drying  prop- 
erty in  an  oil  is  due  to  the  presence  of  unsaturated  fatty 
acids,  which  readily  become  saturated  by  combination 
with  oxygen.  Linseed  oil  is  an  example  of  an  oil  which 
quickly  undergoes  oxidation  and  is  converted  into  a 
varnish.  In  this  case  drying  is  greatly  hastened  by  a 
previous  boiling  of  the  oil. 

Iodine  Value. — The  degree  of  unsaturation  in  a  semi- 
drying  or  drying  oil  can  be  determined  by  the  amount  of 
iodine  it  will  take  up  in  the  formation  of  addition  prod- 
ucts. This  is  known  as  the  iodine  number  or  value  of 
the  oil. 

Hydrogenation. — By  a  process  comparatively  new, 
fats  and  oils  containing  unsaturated  fatty  acids  are  made 
to  take  up  hydrogen  by  catalytic  action  and  become  sat- 


134  HOUSEHOLD   CHEMISTRY 

urated  compounds.  Such  fats  are  now  being  put  on  the 
market  for  edible  purposes  and  for  soap-making. 

Hydrolysis. — The  hydrolysis   of   fats,   as   well   as   of 
esters  in  general,  is  called  saponification.    The  change  is 
a  splitting  of  the  fat  into  its  components — glycerol  and 
fatty  acids — illustrated  by  the  reaction : 
(C^COO),  C3H5  +  3HOH  ~ 

stearin 

3C1TH,,COOH  +  C3H5(OH)3 

stearic  acid  glycerol 

Moisture  alone  will  not  effect  hydrolysis  of  fats  in  any 
definite  length  of  time:  a  catalyst  is  necessary  to  accel- 
erate the  change.  Heat,  acids  or  alkalies,  and  enzymes 
act  as  catalytic  agents.  At  a  temperature  of  200°  or 
more,  water,  e.g.,  superheated  steam,  attacks  glycerides. 
If  dilute  HC1  or  H2SO4  is  used,  the  saponification  occurs 
rapidly  with  less  heat.  Quick  hydrolysis  is  also  brought 
about  by  heating  the  fat  with  an  excess  of  an  alcoholic 
solution  of  caustic  soda  or  potash.  In  this  case  the  fatty 
acid  set  free  unites  with  the  alkali  to  form  soap  (see 
next  page,  and  Chap.  XV).  If  fat-splitting  enzymes  are 
present,  hydrolysis  may  be  brought  about  by  moisture  at 
normal  temperatures.  These  enzymes  occur  in  seeds 
containing  vegetable  oils,  and  during  germination  are 
active  in  changing  the  fat  to  a  form  utilizable  by  the 
embryo.  As  the  quantity  of  enzymes  in  the  filtered  com- 
mercial oils  is  small,  the  per  cent,  of  free  fatty  acid  they 
contain  is  likewise  small  as  a  rule,  and  hydrolysis  does 
not  proceed  if  they  are  protected  from  air  and  moisture, 
or  are  not  in  contact  with  the  organic  material  from 


HOUSEHOLD    CHEMISTRY  135 

which  they  have  been  extracted.  Under  the  reverse  con- 
ditions the  formation  of  free  fatty  acid  may  proceed  to  a 
considerable  degree  even  in  refined  oils. 

Rancidity. — Although  a  fat  or  oil  may  have  an  acid 
reaction,  it  is  not  necessarily  rancid — the  terms  are  not 
synonymous.  Acidity  precedes  rancidity;  the  change  to 
the  latter  state  is  supposed  to  be  due  to  oxidation  of  free 
fatty  acid  by  the  oxygen  of  the  air,  in  the  presence  of 
light.  The  peculiar  taste  of  rancid  fat  is  caused  by  these 
oxidation  products.  Bacterial  action  is  not  necessary  to 
the  change,  for  a  sterile  fat  may  become  rancid,  but  the 
presence  of  foreign  substances  may  favor  enzyme  or 
bacterial  hydrolysis  of  the  glycerides.  Butter  for  this 
reason  easily  becomes  rancid,  as  some  protein  material 
may  be  present. 

Soap-Making  Property. — Fats  hydrolyzed  with  metal- 
lic hydroxides  form  soaps  by  the  further  action  of  the 
free  fatty  acid  with  the  base.  Using  NaOH  or  KOH, 
the  changes  are: 

1 i )  (C17H35COO)3C3H5  +  3HOH  — 

3C17H35COOH  +  C,H5(OH)3. 

(2)  C17H35COOH  +  NaOH  -*  C17H35COONa  -f  H2O. 

sodium  stearate 
or  hard  soap. 

If  KOH  is  used,  a  soft  or  potash  soap  is  made.  With 
Ca(OH)2  an  insoluble  lime  soap,  (C17H35COO)2Ca,  is 
formed.  This  appears  as  an  insoluble  curd  when  soap 
is  used  in  hard  water.  With  PbO  (or  Pb(OH)2),  a 
lead  soap  (C17H35COO)2Pb,  results.  (See  page  138, 
Exp.  9.) 


136  HOUSEHOLD   CHEMISTRY 

EXPERIMENTS  ON  FATS. 

Ultimate  Composition — Hydrogen  and  Oxygen  in  the  Form  of 
Water. — Boil  20-25  drops  of  clear  olive  oil  in  a  clean  dry  test 
tube.  Note  the  watery  deposit  in  the  cooler  part  of  the  tube; 
some  of  this  running  back  will  cause  the  fat  to  crackle. 

Glycerine. — Continue  heating  the  tube  until  dense  fumes  arise 
from  the  boiling  liquid.  This  is  due  to  acrolein,  CH2 :  CH.CHO, 
a  decomposition  product  of  glycerine.  Note  the  odor. 

Cool  the  tube  and  contents  and  reserve  for  next  step. 

Carbon  and  Hydrogen  as  Hydrocarbons  Resulting  from  the 
Breakdown  of  the  Fatty  Acids. — Pour  the  cold  tube  contents 
into  a  clean  dry  porcelain  dish  and  heat  slowly  but  strongly  over 
a  low  flame.  Note  the  gradual  darkening  of  the  liquid  due  to 
freeing  of  carbon  and  the  tarry  coat  on  the  rim  of  the  dish 
(hydrocarbons).  Hold  a  lighted  match  over  the  dish  and  note 
the  inflammable  character  of  the  vapor  (hydrocarbon  gases). 
Extinguish  the  flame  and  continue  the  heating  until  only  a  black 
residue  remains.  This  is  carbon;  prove  it  by  burning  off. 

Extraction  of  Pure  Fat  from  Animal  Sources. — Weigh  out 
10  grams  of  beef  suet  cut  up  in  small  pieces.  Place  in  a  small 
evaporating  dish  and  heat  cautiously,  so  that  no  darkening  of 
the  fat  occurs.  (What  causes  the  spattering?)  When  the 
spattering  has  ceased,  strain  through  muslin  into  a  porcelain 
dish,  squeeze  out  the  cloth  and  reserve  the  liquid  for  tests  on 
fats. 

Transfer  the  residue  to  a  small  mortar,  add  5  cc.  of  strong 
alcohol,  grind  well.  Pour  this  mixture  into  a  small  flask,  wash 
out  the  mortar  with  alcohol  and  add  the  washings  to  the  flask. 
Finally  close  the  flask  with  a  cork,  bearing  a  condenser  tube 
24  inches  long,  support  on  a  ring  stand  over  a  water-bath  and 
boil  for  10  minutes.  When  the  suspended  matter  has  settled, 
uncork  the  flask  and  pour  the  clear  liquid  on  a  small  filter,  allow- 
ing the  filtrate  to  run  into  a  large  test  tube.  To  the  residue  in 
the  flask,  add  20  cc.  of  ether,  insert  the  cork  and  condenser  and 
cautiously  heat  over  hot  water  for  5  minutes.  Then  transfer 


HOUSEHOLD   CHEMISTRY  137 

the  entire  contents  of  the  flask  to  a  small  muslin  filter  and 
collect  the  filtrate  in  the  same  tube  as  before.  Close  the  test 
tube  with  a  loose  cotton  plug,  allow  it  to  stand  until  crystals 
deposit  from  the  liquid.  Examine  these  under  the  microscope 
and  draw  a  diagram  of  them.  Wash  the  residue  from  the  last 
filtration  with  a  little  ether,  squeeze  out,  spread  on  the  muslin 
and  dry.  Take  it  up  with  a  little  water,  add  a  few  drops  of 
Millon's  reagent,  and  heat  gently.  A  red  color  indicates  protein 
matter. 
Make  the  following  tests  on  the  rendered  (extracted)  fat: 

1.  Solubility. — Test  the  solubility  of  small  portions  of  fat  in 
separate  test  tubes  with  water  hot  and  cold,  alcohol  hot  and 
cold,  and  in  hot  Na-jCOs,  shaking  the  mixtures  well.    Record  the 
results. 

2.  Absorption. — Place  a  small  piece  of  fat  on  a  filter  paper  and 
heat  until  the  fat  melts ;  note  the  result. 

3.  Formation  of  Acrolein. — Rub  up  a  small  piece  of  fat  in  a 
mortar  with  some  acid  potassium  sulphate,  transfer  to  a  clean, 
dry  test  tube  and  heat  cautiously;  note  the  peculiar  disagreeable 
odor  of  acrolein  and  the  reducing  effect  of  the  aldehyde  on  a 
strip  of  filter  paper  moistened  with  ammoniacal  silver  nitrate. 

4.  Emulsification. — Shake  together  a  few  centimeters  of  cod- 
liver  oil  and  dilute  sodium  carbonate.    Notice  the  resulting  white 
mass  which  is  called  an  emulsion;  what  well  known  liquid  is 
similar  in  appearance?     Examine  two  or  three  drops  of  this 
emulsion  under  the  microscope  and  note  the  character  of  the 
compound. 

Repeat  the  experiment,  using  a  few  drops  of  olive  oil  and  a 
solution  of  albumin. 

5.  Saponification  with  Alkali. — To  about  I  gram  of  fat  in  a 
low  flask  fitted  with  a  reflux  condenser  add  25  cc.  of  alcoholic 
potash  solution,  and  boil.    Replace  the  liquid  lost  by  evaporation 
with  alcohol.     As  the  heating  progresses,  the  mixture   should 
become  homogeneous ;  if  it  does  not,  add  a  little  more  potash  and 
boil  until  clear   (saponified).     Remove  the  cover  and  evaporate 
the  bulk  of  the  alcohol,  finally  adding  hot  water  and  heating 


138  HOUSEHOLD   CHEMISTRY 

until  all  alcoholic  odor  has  disappeared.    Cool  the  liquid,  divide 
into  three  parts  and  use  in  (6)  and  (8). 

6.  Precipitation  and  Decomposition  of  Soap. — To  one  portion 
add  a   saturated   solution  of   salt;   notice  the  curdy  precipitate 
(soap).    Filter  off  this  precipitate,  try  its  solubility  in  cold  water. 
Acidify  another  portion  of  the  dissolved  soap  with  dilute  sul- 
phuric acid.    Note  the  curdy  precipitate  (fatty  acids).    Boil  the 
mixture  until  clear,  filter  and  use  in  test  7. 

7.  Test  the  solubility  of  the  fatty  acids  in  water,  warm  alcohol 
and  sodium  carbonate  solution.    Record  results. 

8.  Formation  of  Lime  Soap. — Add  an  excess  of  a  solution  of 
lime  water  to  another  portion  of  the  soap  solution  and  notice 
the  greasy  precipitate,   which  is  insoluble  in  warm  water  and 
alcohol  (lime  soap,  produced  by  hard  water). 

9.  Formation  of  Lead  Soap. — Heat  a  small  quantity  of  lard  or 
tallow  for  some  time  in  an  evaporating  dish,  with  lead  oxide, 
PbO,  and  a  little  water ;  filter  off  the  watery  liquid  and  evaporate 
a  small  quantity  on  a  platinum  foil.    Note  the  characteristic  odor 
of  acrolein,  proving  the  presence  of  glycerine. 

10.  Determination  of  Free  Fatty  Acid. — Take  a  weighed  amount 
of  olive  oil  (about  i  gram),  add  about  25  cc.  of  alcohol  which 
has  been  neutralized  with  N/NaOH  (one  drop  will  probably  be 
sufficient)    and   boil.     While  hot,   titrate   against   N/io   NaOH. 
Calculate  the  percentage  of  fatty  acid  in  the  sample  in  terms  of 
oleic  acid. 

11.  Koettstorfer  Number. — Weigh  out  2.5  grams  of  fat  in  a 
low  flask.     Add  25  cc.  of  approximately  N/4  alcoholic  potash 
solution,  cover  with  a  watch  glass  and  heat  on  a  water  bath  until 
the  fat  is  completely  saponified.     Cool,  and  titrate  back  excess 
of  alkali  with  N/2  HC1.    Make  a  blank  test  in  a  similar  manner 
on  the   alcoholic  potash   and   calculate  the   per   cent,   of   alkali 
absorbed  in  saponification.    This  test  is  used  in  the  case  of  an 
unknown  fat  to  determine  its  combining  ratio  with  alkali. 

12.  Iodine  Test. — Into  each  of  two  test  tubes  pour  20  drops  of 
the  oil  under  test.     Dissolve  the  oil  with  about  5  cc.  of  chloro- 
form.   Add  4  or  5  drops  of  iodine  solution  to  one  of  the  samples ; 


HOUSEHOLD   CHEMISTRY  139 

cork  and  shake.  To  insure  an  excess  of  iodine,  test  by  placing 
I  drop  of  the  mixture  on  filter  paper.  Observe  the  change  in 
color  in  the  tube  to  which  iodine  has  been  added,  in  case  the  oil 
contains  unsaturated  fatty  acids. 

13.  Extraction    of    Fats    from    Cereals    or    Nuts. — Grind    the 
sample  to  a  fine  powder  and  dry  in  an  air  bath  at  ioo°-i05°  to 
constant  weight.    Weigh  from  2  to  3  grams  of  the  dried  material, 
place  in  an  extraction  shell,  and  cover  loosely  with  absorbent 
cotton.     Extract  in  a  Soxhlet  apparatus  with  water-free  ether 
for  about  16  hours,  allowing  the  extract  to  run  into  a  weighed 
flask.     Use  a  water-bath,  or  better,  an  electric  plate,  to  avoid 
danger  from  overheating  the  ether.     Finally  evaporate  the  con- 
tents of  the  flask  to  constant  weight  and  estimate  the  per  cent, 
of  fatty  material  removed  in  the  ether  extract. 

14.  Special   Tests    for   Drying   Oils. — (a)    Becchi's   Test. — To 
5  cc.  of  the  oil  in  a  6-inch  test  tube,  add  an  equal  volume  of 
silver  nitrate  dissolved  in  alcohol   (i  per  cent,  solution);  close 
the  test  tube  with  a  cotton  plug  and  keep  it  in  boiling  water  for 
10  to  15  minutes.    A  darkening  of  the  mixture  indicates  cotton- 
seed oil.    The  acids  in  cotton-seed  oil  quickly  reduce  the  silver 
nitrate;  those  in  olive  oil  only  after  some  time. 

(b)  Halphen's  Test. — To  5  cc.  of  the  oil  in  a  6-inch  test  tube 
add  5  cc.  of  amyl  alcohol  and  5  cc.  of  carbon  disulphide  contain- 
ing a  little  free  sulphur.  Close  the  test  tube  with  a  loose  cotton 
plug  and  keep  in  hot  water  away  from  an  open  flame  for  l/2  hour. 
A  red  coloration  indicates  cotton-seed  oil.  This  is  a  very  deli- 
cate test. 

BUTTER.  SPECIFIC  TESTS. 

Wash  a  teaspoonful  of  butter  in  several  waters  until  free  from 
salt.  Prove  this  by  making  the  silver  nitrate  test  on  the  last 
washing.  Note  any  difference  between  the  first  and  last  wash- 
ings when  tested  with  litmus  paper.  Explain.  Dry  the  washed 
butter  between  filter  paper,  melt,  and  dissolve  in  gasoline.  Filter, 
and  wash  the  residue  on  the  paper  with  gasoline  until  a  drop  of 
the  washings  evaporated  on  paper  leaves  no  greasy  stain;  dry 
10 


I4O  HOUSEHOLD   CHEMISTRY 

and  note  the  character  of  the  residue  (curd).  Cautiously  heat 
this  in  a  test  tube  with  lime ;  observe  the  odor  produced  and  hold 
in  the  fumes  a  piece  of  moistened  red  litmus  paper  and  note  the 
result. 

Spoon  Test — Gently  heat  a  piece  of  butter  about  the  size  of 
a  cherry  in  a  tablespoon.  If  it  froths  without  spattering,  it  is 
pure  butter.  If  it  foams  and  spatters  it  is  renovated  butter;  if 
it  spatters  only,  it  is  oleomargarine. 

Butyric  Acid  Test — In  a  4-ounce  narrow  neck  flask,  fitted  with 
a  one-holed  rubber  stopper,  put  about  2^4  grams  of  butter. 
Saponify  with  caustic  potash.  Decompose  the  resulting  product 
with  dilute  sulphuric  acid  in  excess.  Then  distill  the  product 
gently,  using  a  bent  tube  condenser.  Butyric  acid  will  distill  at 
about  the  temperature  of  boiling  water.  Allow  the  distillate  to 
drop  into  a  funnel  containing  moist  filter  paper.  This  causes 
the  retention  of  fatty  acids  (other  than  butyric).  Below  the 
funnel  is  placed  an  Erlenmeyer  flask  containing  distilled  water 
made  alkaline  by  adding  2  drops  of  10  per  cent.  NaOH,  and 
tinted  with  phenolphthalein.  The  disappearance  of  the  pink  color 
will  occur  when  sufficient  butyric  acid  has  passed  over  to  neu- 
tralize the  soda. 


CHAPTER  X. 


PROTEINS. 

The  proteins  are  the  chief  nitrogenous  constituents  of 
both  plants  and  animals.  Owing  to  their  complex  nature, 
the  exact  chemical  structure  of  protein  bodies  has  not 
been  determined,  but  they  are  regarded  as  anhydrides  of 
amino  acids,  since  they  yield  these  acids  on  hydrolysis. 

The  elementary  composition  of  all  proteins  includes 
carbon,  hydrogen,  oxygen  and  nitrogen,  with  sulphur  in 
typical  forms.  These  elements  are  found  in  the  follow- 
ing average  ratio:  Carbon  51-55  per  cent.,  hydrogen  7 
per  cent.,  nitrogen  15-19  per  cent.,  oxygen  20-30  per 
cent.,  sulphur  0.4-2.5  per  cent.  In  addition,  phosphorus 
is  frequently  found  in  direct  or  indirect  combination 
with  the  protein  molecule,  and  iron  and  calcium  appear 
in  some  cases. 

The  large  size  of  the  protein  molecule  can  be  judged 
by  the  formula  assigned  to  globin,  one  of  the  simplest 
forms :  C72QH1174N194S3O2i4. 

Classification. — Proteins  are  classified  principally  on 
the  basis  of  differences  in  solubilities  and  hydrolysis. 
The  classification  which  follows  is  the  one  recommended 
by  the  American  Physiological  Society  and  the  American 
Society  of  Biological  Chemists: 


142 


HOUSEHOLD   CHEMISTRY 


Proteins 


Non-proteins 


Simple 


Conjugated 


Derived 


Extractives 
Amides 
Aniino  acids 


f  Albumins 
Globulins 
Glutelins 
Alcohol 

Solubles 
Albuminoids 
Histones 
Protamines 

f  Nucleoproteins 
Glycoproteins 
Phosphopro- 

teins 

Haemoglobins 
Lrfscithoproteins 

Primary 
derivatives 


Secondary 
derivatives 


{Proteans 
Metaproteins 
Coagulated 
proteins 

IProteoses 
Peptones 
Peptides 


In  this  classification  the  group  called  simple  proteins 
hydrolyze  to  ammo  acids,  conjugated  proteins  yield  pro- 
tein decomposition  products  and  some  other  body.  This 
latter  substance  is  nuclein  in  the  nucleoproteins,  a  car- 
bohydrate in  the  glycoproteins,  a  phospho  body  in  the 
phosphoproteins,  haematin  in  haemoglobins,  and  a  fatty 
substance  in  lecithoproteins.  The  derived  proteins  are 
changed  forms  produced  by  the  action  of  heat,  acids  or 
alkalies,  or  enzymes. 

Occurrence  and  Solubilities. — Albumins. — In  plant  and 
animal  bodies,  as  egg,  plant,  and  serum  albumin.  Sol- 
uble in  pure  water,  precipitated  by  complete  saturation 


HOUSEHOLD   CHEMISTRY  143 

with  ammonium  sulphate,  but  not  by  saturated  mag- 
nesium sulphate  or  sodium  chloride. 

Globulins. — In  animal  bodies  fibrinogen  and  derived 
fibrin,  and  myosinogen  and  derived  myosin  show  glob- 
ulin characteristics.  Other  forms  are  egg  serum  and 
lact-globulin.  Examples  in  plants  are  legumin  and 
edestin.  Globulins  are  not  soluble  in  water  or  in  dilute 
acids,  but  dissolve  in  dilute  solutions  of  inorganic  salts. 
They  are  precipitated  by  saturation  with  magnesium  sul- 
phate or  sodium  chloride,  or  by  half  saturation  with 
ammonium  sulphate. 

Glutelins. — Found  in  cereals;  as  glutenin  in  wheat 
and  oryzenin  in  rice.  Insoluble  in  all  neutral  solvents 
but  readily  soluble  in  very  dilute  acids  and  alkalies. 

Alcohol-Solubles  (Prolamines). — Gliadin  (in  wheat, 
combining  with  glutenin  to  form  gluten  in  a  dough  mix- 
ture) ;  zein  (maize) ;  hordein  (barley).  Insoluble  in 
water  and  absolute  alcohol,  soluble  in  70-80  per  cent, 
alcohol. 

Albuminoids  (Scleroproteins). — Keratins  of  horn, 
hair,  nails,  egg  membrane;  collagen  of  white  connective 
tissue,  and  elastin  of  yellow  elastic  tissue,  yielding 
gelatin;  silk  gelatin  and  fibroin.  Insoluble  in  all  neutral 
solvents.  Gelatin,  a  derived  form,  dissolves  in  hot 
water. 

Histones. — Found  combined  with  nucleic  acid,  form- 
ing certain  nucleoproteins,  e.  g.,  in  the  nuclei  of  blood 
corpuscles  of  birds,  in  the  thymus  gland,  etc.  Soluble  in 
water,  insoluble  in  very  dilute  NH4OH. 


144  HOUSEHOLD   CHEMISTRY 

Protamines. — Simple  in  composition;  found  in  con- 
junction with  nucleic  acid  in  spermatozoa  of  certain  fish. 
Soluble  in  water. 

Nucleo proteins. — Widely  distributed;  form  chief  pro- 
tein constituent  of  nuclei;  contain  nucleic  acid  combined 
generally  with  albumins,  histones,  or  protamines. 

Glycoproteins. — Ovo-mucoid;  mucin  of  mucous  mem- 
brane. Soluble  in  dilute  alkalies;  mucins  reprecipitated 
by  acetic  acid,  mucoids  are  not. 

Phosphoproteins. — Caseinogen  of  milk,  vitellin  of  egg 
yolk.  Insoluble  in  water;  readily  soluble  in  alkalies, 
forming  salts;  precipitated  by  acids. 

Haemoglobins  (Chromoproteins). — Chromogenic  sub- 
stances, e.  g.,  haemoglobin  in  blood. 

Lecithoproteins  (Lipoproteins). — These  are  nitrogen- 
ous bodies  combined  with  a  fat  radical.  Examples  are 
lecithans  and  phosphatides.  Occur  in  yolk  of  egg,  milk, 
etc. 

Proteans. — Occur  as  insoluble  products  apparently  re- 
sulting from  the  incipient  action  of  water,  very  dilute 
acids,  or  enzymes. 

Metaproteins. — Found  in  partial  hydrolysis  of  pro- 
teins by  the  action  of  acids  or  alkalies;  known  as  acid 
or  alkali  albumin  or  globulin,  etc.  Insoluble  in  water, 
soluble  in  dilute  acids  or  alkalies,  precipitated  by  alcohol. 

Coagulated  Proteins. — See  coagulation. 

Proteases. — Intermediate  products  of  protein  diges- 
tion. Soluble  in  water,  precipitated  by  alcohol  or  sat- 
uration with  ammonium  sulphate. 


HOUSEHOLD   CHEMISTRY  145 

Peptones. — Further  products  of  proteolysis.  Soluble 
in  water  and  saturated  ammonium  sulphate.  Precipi- 
tated by  alcohol. 

Peptids. — Simple  hydrolytic  products  of  the  protein 
molecule,  which  readily  yield  two  or  more  amino  acids 
on  further  hydrolysis.  An  example  is  glycyl-glycine 
H2N.CH2.CO.NH.CH2COOH. 

Extractives. — Creatin  and  creatinin,  found  in  muscle. 

Amides. — Urea,  asparagine  in  asparagus. 

Amino  Acids. — Simple  decomposition  products  of  the 
proteins. 

Properties. — i.  General. — Proteins  are  bodies  of  high 
molecular  weight,  optically  active,  colloidal,  and  gen- 
erally colorless.  Most  proteins  are  amorphous,  but  some 
have  been  obtained  in  crystalline  form,  e.  g.,  edestin 
from  hemp  seed.  They  are  both  acid  and  basic  in  re- 
action. 

2.  Coagulation. — Many  proteins,  especially  albumins 
and  globulins,  undergo  a  precipitation  known  as  coagu- 
lation, on  heating  their  aqueous  solutions.  The  chem- 
ical change  between  the  water  and  the  protein  is  not 
clearly  understood.  Complete  coagulation  is  only  ob- 
tained in  slightly  acidified  solution.  Coagulated  proteins 
are  insoluble,  and  cannot  be  reconverted  into  the  original 
protein  substance.  Different  factors  affect  rapidity  of 
coagulation,  so  that  a  range  of  temperature  is  usually 
given  as  the  coagulation  point  of  any  specified  protein. 
The  hardening  effect  of  alcohol  on  proteins  is  a  form  of 
coagulation. 


146  HOUSEHOLD   CHEMISTRY 

3.  Curdling. — This  term  describes  a  precipitation  of 
protein  material  by  acids  or  certain  salt  solutions,  espec- 
ially observed  in  the  case  of  milk.     The  caseinogen  in 
milk  exists  as  a  soluble  calcium  caseinogenate,  which  is 
broken  up  by  the  action  of  lactic  or  other  acids  and  the 
caseinogen  is  thrown  out  of  solution — i.  e.,  the  milk  has 
curdled.     The  calcium  caseinogenate  can  be  precipitated 
by  salting  out  with  sodium  chloride. 

4.  Clotting. — Certain  conjugated   proteins   undergo   a 
change  properly  known  as  clotting,  which  occurs  only 
through  enzyme  action.    As  seen  in  milk,  the  caseinogen 
is  acted  upon  by  rennin,  which  produces  a  soluble  hy- 
drolytic  product,  casein.     The  lime  salt  of  casein  is  in- 
soluble, and  clotting  can  take  place,  therefore,  only  if 
soluble  calcium  salts  are  present  to  form  the  insoluble 
calcium  caseinate.     This  is  the  clot  produced  in  junket 
and  cheddar  cheese  making.     A   similar  change   takes 
place  in  the  clotting  of  the  fibrinogen  of  blood,  and,  as 
far  as  is  known,  in  the  muscle  tubes  after  death,  caus- 
ing rigor  mortis. 

5.  Hydrolysis. — The    hydrolysis    of    simple    proteins 
yields    the    following    as    the    principal    decomposition 
products : 

Protein  »-*•  Metaprotein  •-*  Proteoses  —»  Pep- 
tones »-*  Peptides  «»-»>  Amino  acids. 

Most  albumins  and  globulins  also  yield  a  carbohydrate 
substance,  which  in  several  cases,  e.  g.,  egg  globulin,  has 
been  identified  as  glucosamin. 

Phosphoproteins    split    off    an    insoluble    phosphorus 


HOUSEHOLD    CHEMISTRY 


147 


compound  in  the  early  stages  of  hydrolysis,  which  be- 
comes soluble  later  in  digestion.  To  this  substance  the 
names  para-  or  pseudo-nuclein  have  sometimes  been 
given. 

Nucleoproteins  hydrolyze  as  follows: 

Nucleoprotein 

/      \ 

Protein  Nuclein 

x\ 


Protein 


Nucleic  acid 
\ 


Meta  phosphoric 
acid 


Bases 


Carbohydrate : 
Pentoses 
Hexoses 


Purin  : 

Adenin 

Guanin 

Hypoxanthin 

Xanthin 
Pyrimidin  : 

Uracil 

Thymin 

Cytosin 


In  the  laboratory,  complete  hydrolysis  may  be  ef- 
fected by  boiling  with  concentrated  HC1  for  6  to  12 
hours,  or  with  25-33  per  cent.  H2SO4  for  12  to  20  hours. 

TESTS  ON  PROTEINS  | 

Ultimate  Composition — i.  Nitrogen  as  Ammonia. — Mix  some 
dried  egg  albumin  with  lime  and  moisten  sufficiently  to  roll  into 
small  balls  with  the  fingers.  Place  two  or  three  of  these  balls 
in  a  dry  test  tube,  heat  and  hold  in  the  vapors  a  piece  of 
moistened  red  litmus  paper.  Note  the  result.  Let  the  paper  dry 
and  observe  the  change. 

2.  Sulphur  as  Hydrogen  Sulphide. — Test  the  fumes  with  a  piece 
of  filter  paper  moistened  with  lead  acetate  and  note  the  result. 


148  HOUSEHOLD   CHEMISTRY 

3.  Hydrogen  and  Oxygen  as  Water. — Observe  the  condensa- 
tion of  water  in  the  cooler  part  of  the  tube. 

4.  Carbon. — Observe   the   blackening   effect   produced   by   the 
freeing  of  the  carbon. 

5.  Phosphorus. — Place  the  well  charred  residue  in  a  small  por- 
tion dish,  moisten  with  concentrated  HNOs  and  heat  gently  until 
excess  of  acid  has  been  vaporized,  then  heat  strongly  until  the 
carbon  has  been  entirely  consumed.     Cool  the  residue,  moisten 
with  HNO3,  add  water,  boil  and  filter  if  necessary.     Test  the 
clear  liquid  with  ammonium  molybdate. 

For  the  purpose  of  making  general  and  specific  tests  on  the 
proteins,  a  solution  of  egg  albumin  prepared  according  to  the 
following  directions  is  recommended. 

Preparation  of  Egg  Albumin — Carefully  break  a  fresh  egg, 
allow  the  clear  white  to  run  into  a  porcelain  dish  and  set  the 
yolk  aside  for  future  use.  Cut  the  white  with  scissors  or  grind 
with  sand  and  place  a  small  portion  in  a  wide-mouthed  stoppered 
bottle,  add  10  volumes  of  distilled  water,  shake  until  it  froths 
and  invert  over  a  small  casserole  of  water.  When  the  froth  and 
insoluble  protein  particles  float  on  the  surface,  carefully  with- 
draw the  cork  and  allow  some  of  the  liquid  to  mix  with  the  water 
in  the  casserole.  The  liquid  will  probably  be  opalescent,  due  to 
traces  of  globulin;  if  strongly  so  filter  through  muslin,  test  the 
fluid  with  litmus  paper  and  if  alkaline  neutralize  with  weak  acetic 
acid  (2  per  cent). 

i.  General  Testa — (a)  Nitric  Acid  (Xanthoproteic  reaction).— 
To  a  small  portion  of  the  filtered  liquid,  add  strong  nitric  acid. 
This  forms  a  white  precipitate  which  turns  yellow  on  heating; 
now  cool  and  add  ammonia — it  becomes  orange.  Compare  with 
spots  on  the  skin  or  woolen  cloth  produced  with  HNO3. 

(&)  Biuret  Test. — To  I  inch  of  10  per  cent,  caustic  soda  or 
potash,  add  dilute  copper  sulphate,  drop  by  drop,  until  a  faint 
blue  color  but  no  precipitate  remains  in  the  liquid  after  shaking; 
now  add  the  protein  solution.  A  violet  color  indicates  protein; 
a  pink,  peptone. 


HOUSEHOLD   CHEMISTRY  149 

(c)  Precipitation  Tests. — Solutions  of  the  proteins  are  precipi- 
tated by  the  following  reagents : 

Alcohol. 
Tannic  acid. 
Picric  acid. 

(d)  Coagulation  by  Heat. — Heat  some  of  the  fluid  to  boiling 
and  at  the  same  time  add,  drop  by  drop,  very  dilute  acetic  acid 
(2  per  cent.)  as  long  as  a  precipitate  forms;  note  that  this  pre- 
cipitate does  not  appear  unless  the  solution  is  acid.    Attempt  to 
filter  some  of  the  albumin  through  a  wet  filter  paper;  prove  by 
one  of  the  above  tests  that  no  protein  is  in  the  filtrate. 

2.  Special  Tests  for  Abumins  and  Globulins — (a)  Millon's. — 
To  a  small  portion  of  the  solution,  add  Millon's  reagent  and 
heat.    This  forms  a  white  precipitate  which  turns  red  on  cool- 
ing, or  gives  a  red  color  if  only  a  trace  of  protein  is  present. 
Avoid  using  Millon's  in  the  presence  of  sodium  chloride. 

(6)  Heller's  Test. — Place  some  strong  nitric  acid  in  a  test  tube 
and  allow  a  solution  of  albumin  to  flow  gently  down  the  sides  of 
the  tube;  a  white  ring  of  precipitated  albumin  forms  at  the 
junction. 

(c)  M eta-phosphoric  Acid  Test. — Add  a  solution  of  albumin 
to  a  very  little  cold  freshly  prepared  metaphosphoric  acid  and 
note  the  precipitate  formed. 

(d)  Adamkiewicz's  Test. — Add  the  protein  solution  to  a  mix- 
ture of   i   volume   concentrated   ILSCX  and  2   volumes   glacial 
acetic  acid.    Heat.    A  red  violet  color  appears.    Gelatin  does  not 
give  this  reaction. 

(?)  Precipitation  Tests. — To  portions  of  the  solution  in  sepa- 
rate test  tubes  add : 

Acetic  acid  and  potassium  ferrocyanide. 
Mercuric  chloride. 
Lead  acetate. 

3.  Separation  Tests — (a)  To  a  portion  of  the  solution,  add  an 
excess  of  dry  crystallized  ammonium  sulphate,  shake  vigorously. 
Albumin  and  globulin  will  be  precipitated,  probably  in  a  changed 


I5O  HOUSEHOLD   CHEMISTRY 

form.     Filter  through  a  good  grade  of  paper  and  make  biuret 
test. 

(&)  To  a  portion  of  the  solution,  add  dry  sodium  chloride  or 
magnesium  sulphate  to  saturation.  Globulin  is  precipitated. 
Filter,  and  test  filtrate  with  either  nitric  acid  or  Heller's  test. 
This  is  a  somewhat  imperfect  method  of  separating  albumin  and 
globulin. 

4.  Indiffusibility — Place  some  of  the  solution  in  a  dialyzer  of 
parchment  paper  and  suspend  the  whole  in  a  beaker  of  distilled 
water.     Test  the  water  subsequently   for  chlorides   with   silver 

•nitrate  and  also  for  protein  by  the  biuret  test. 

5.  Proteolysis.— (a)  Add  Metaprotein. — To  undiluted  egg  white 
add  concentrated  HC1;  note  the  copious  precipitate  of  albumin 
(coagulated).    Heat  gently  until  the  mass  dissolves  resulting  in 
a  violet  solution.    Cool  some  of  this  liquid,  testing  separate  por- 
tions as  follows : 

1.  Heat  to  70°  by  placing  the  test  tube  in  hot  water  and  rais- 
ing the  temperature  gradually.    Does  any  coagulation  appear? 

2.  Neutralize  with  dilute  caustic  soda,  filter  and  make  the  biuret 
test  on  the  residue. 

3.  Add  a  few  drops  to  15-20  cc.  saturated  sodium  chloride. 

4.  Add  a  few  drops  to  15-20  cc.  95  per  cent,  alcohol. 

(&)  Alkali  Metaprotein. — Treat  undiluted  white  of  egg  with 
strong  alkali;  note  the  clear  jelly-like  mass  which  results.  Heat 
to  clear  solution  and  dilute  some  of  this  with  water.  Make  the 
following  tests : 

1.  Heat  to  70°,  as  above. 

2.  Neutralize  with  dilute  acetic  acid,  filter  and  make  the  biuret 
test  on  the  residue. 

3.  Add  a  few  drops  to  15-20  cc.  saturated  sodium  chloride. 

4.  Add  a  few  drops  to  15-20  cc.  of  95  per  cent,  alcohol. 
NOTE. — Weaker  solutions  of  albumin  are  converted  to  meta- 

protein  by  treating  with  a  few  cubic  centimeters  of  very  weak 
alkali  or  acid  (o.i  per  cent.)  at  about  40°  for  some  time. 


HOUSEHOLD   CHEMISTRY  151 

Proteose  and  Peptone.— The  action  of  pepsin  is  hydrolytic  and 
produces  both  proteose  and  peptone — a  case  similar  to  the  pro- 
duction of  dextrin  and  glucose  from  starch.  Make  a  pepsin 
digestion  experiment  as  follows  : 

Coagulate  egg  albumin  by  heat.  Cut  into  small  wedge-shaped 
pieces,  put  into  3  test  tubes  and  treat  as  follows : 

1.  Cover  with  highly  dilute  hydrochloric  acid  (0.2  per  cent.). 

2.  Add  a  small  amount  of  neutralized  pepsin  solution  (o.i  per 
cent.). 

3.  Add  a  mixture  of  equal  parts  of  pepsin  and  hydrochloric 
acid. 

Place  all  3  tubes  in  a  beaker  of  cold  water,  heat  to  body  tem- 
perature and  note  the  time  they  take  to  clear;  also  observe 
whether  the  mass  swells ;  finally  filter  all  three  and  test  the  clear 
filtrates  for  peptone  by  the  biuret  test. 

Globulins — Globulin  from  the  White  of  Egg. — Saturate  some 
of  the  undiluted  solution  with  dry  magnesium  sulphate,  grinding 
the  mass  in  a  mortar.  Observe  the  precipitate  of  globulin,  filter 
and  test  the  filtrate  for  protein.  Now  pour  water  through  the 
insoluble  mass  on  the  filter  and  test  the  extract  for  proteins. 
Explain.  The  yield  of  globulins  obtained  from  this  source  is 
very  small  and  the  following  method  is  preferable : 

Globulin  {Edestin)  from  Hemp  Seed. — Extract  dry,  ground 
hemp  seed  with  sufficient  5  per  cent,  solution  of  sodium  chloride 
to  cover  it  well,  first  grinding  the  mass  in  a  mortar,  then  heat- 
ing it  for  about  half  an  hour  at  60°.  Keep  the  mixture  at  this 
temperature  and  test  as  follows : 

1.  Filter  a  portion  into  a  warm  test  tube,  through  a  filter  just 
previously  washed  with  hot  5  per  cent.  NaCl.     Notice  the  clear- 
ness of  the  filtrate.     Cool  under  running  water  and  observe  the 
precipitate    of    crystallized    edestin.      Filter    off    a    portion    and 
observe  the  crystals  under  the  microscope.    Warm  the  remainder 
gently,  and  cool  again.    What  happens? 

2.  Learn  the  solubilities  of  edestin  by  filtering  a  few  drops  of 
the  clear  solution  as  in  (i)  into  (a)  water,  (b)  alcohol,  (c)  satu- 
rated NaCl,  (d)  5  per  cent.  NaCl  (all  at  60°). 


152  HOUSEHOLD   CHEMISTRY 

3.  Filter,   and   heat   gently  over   hot  water  until   coagulation 
appears.    What  is  the  coagulation  temperature? 

4.  Make  biuret  and  Heller's  tests  on  the  clear  filtrate. 

Yolk  of  Egg — Separation  of  Fat  and  Vitellin. — Place  one-half 
the  yolk  of  a  fresh  egg  in  a  broad  6-inch  test  tube,  add  twice  its 
bulk  of  95  per  cent,  alcohol,  cork,  shake  vigorously,  and  place  in 
water  at  55°  to  60°.  When  the  mixture  has  separated  into  layers, 
decant  the  clear  upper  layer  through  a  filter  into  a  clean  porce- 
lain dish,  and  reserve  for  future  use.  Repeat  with  one  or  two 
further  extractions  until  the  residue  in  the  tube  is  nearly  white. 
Finally  transfer  it  to  a  filter,  wash  with  another  portion  of  warm 
alcohol,  and  dry  over  warm  water.  The  granular  mass  resulting 
is  principally  vitellin.  Proceed  as  follows : 

(1)  Fat. — Evaporate  the  alcohol  extract  over  hot  water  until 
no  odor  of  alcohol  remains.    Note  the  yellow  liquid  oil.    Take  a 
portion  and  test  for  a  fat.    Add  a  few  drops  of  HNOs  to  the 
remainder  and  burn  to  ash ;  divide  the  ash  in  two  portions  and 
take  up  with  a  few  drops  of  concentrated  HC1  and  HNO3  respec- 
tively, add  a  little  water  to  each  and  heat.    Filter  if  necessary, 
test  the  HC1  portion  for  iron  with  ammonium  thiocyanate  and 
the  HNO3  portion  for  phosphoric  acid  with  ammonium  molybdate. 

(2)  Vitellin. — Mix  thoroughly  with  5  per  cent.  NaCl  solution, 
keeping  the  mixture  at  60°  for  15  minutes.    Filter  a  few  drops 
into 

(a)  A  large  bulk  of  water  made  faintly  acid  with  acetic 

acid. 

(6)  95  per  cent,  alcohol. 
(c)  Saturated  salt  solution. 
What  are  the  solubilities  of  vitellin? 

Heat  another  portion  of  the  filtrate  to  coagulating  point. 
What  is  it? 

Make  the  nitric  acid  or  Heller's  test  on  another  portion. 
Shell — i.  Examine  a  portion  of  the  shell  under  the  low  power 
of  a  microscope;  note  the  physical  character.     Treat  a  portion 
of  the  shell  with  silicate  of  soda  solution  (10  per  cent.)  ;  when 


HOUSEHOLD   CHEMISTRY  153 

dry  examine  as  before.     (Silicate  of  soda  is  used  for  preserving 
eggs.) 

2.  Crush  and  grind  the  shell,  thoroughly  extract  with  warm 
water,  dissolve  the  extracted  mass  with  dilute  hydrochloric  acid. 
Note  the  effervescence.    Hold  in  the  fumes  a  drop  of  limewater 
on  the  end  of  a  glass  rod  and  note  the  clouding.    What  gas  is 
formed?    Filter  the  HC1  solution  and  make  slightly  alkaline  with 
ammonia,  add  ammonium  oxalate  and  note  the  white  precipitate 
of   calcium   oxalate,   insoluble   in   acetic   acid.     From   the   data 
found  give  the  composition  of  the  shell  and  the  changes  which 
have  taken  place. 

3.  Allow  an  egg  to  stand  in  strong  vinegar  for  several  hours, 
remove,  wash  in  one  change  of  water,  and  note  the  peculiar  con- 
dition of  the  egg.    Examine  the  acid  liquid  as  in  the  preceding 
experiment. 

4.  Examine  equal  portions  of  the  yolk  and  the  white  of  egg, 
separately,  for  sulphur  by  mixing  with  lime  and  testing  with  the 
lead  acetate  method  given  under  proteins.     Which  do  you  think 
contains  the  greater  amount  of  sulphur? 

5.  Weigh  an  egg  accurately  and  repeat  the  weighing  for  five 
or  six  succeeding  days.    Record  the  results  and  explain. 

For  the  average  composition  of  the  egg,  see  Sherman:  Food 
Products. 

GELATIN. 

By  prolonged  boiling  with  water  gelatin  is  produced 
from  collagen,  which  is  a  protein  occurring  in  the  con- 
nective tissue.  The  sources  of  both  glue  and  gelatin  are 
skin,  bones,  hoofs,  hides,  etc.,  but  the  latter  should  differ 
from  glue  both  as  to  the  condition  of  the  raw  material 
and  the  care  used  in  the  processes  of  manufacture. 

TESTS. 

Place  small  pieces  of  gelatin  in  contact  with  cold  water  and 
note  any  change  which  takes  place,  then  slowly  heat  the  mixture 


154  HOUSEHOLD   CHEMISTRY 

to  boiling ;  does  it  coagulate  ?  Cool  a  portion  of  the  liquid ;  what 
happens?  Test  the  remainder  of  the  warm  solution,  divided  into 
10  parts,  with : 

1.  Dilute  hydrochloric  acid. 

2.  Alcohol. 

3.  Acetic  acid  or  lemon  juice. 

4.  Picric  acid. 

5.  Acetate  of  lead. 

6.  Salt  and  tannin. 

7.  Heller's  test. 

8.  Biuret  test. 

9.  Adamkiewicz's  reaction. 

10.  Boil  a  water  solution  of  gelatin  for  some  time.  Cool,  and 
test  its  gelatinizing  power.  Gelatin  is  hydrolyzed  by  prolonged 
boiling,  and  will  not  gelatinize. 

To  estimate  the  quality  of  commercial  gelatins,  make  the  fol- 
lowing tests : 

1.  The  amount  of  ash  should  not  exceed  2  per  cent.     Burn  a 
weighed   sample   to   ash   of   constant   weight   and   estimate   the 
amount. 

2.  Soak  samples  4  hours,  then  make  into  a  jelly  by  heating. 
Note  odor:    it  should  not  be  offensive.     Expose  a  5  per  cent, 
solution  to  the  air  2  days.    Note  odor. 

3.  Test  gelatinizing  power  by  comparing  the  firmness  of  jelly 
made  by  different  samples  under  the  same  conditions. 

4.  Make  comparative  biuret  tests.    The  color  should  be  violet. 

5.  Make  Millon's  test.    There  should  be  little  or  no  response. 

6.  Try  litmus  paper  reaction.    It  should  not  be  alkaline. 

BONES. 

Bony  tissue  consists  of  a  mixture  of  mineral  matter 
(largely  phosphate  of  lime)  with  protein  (ossein).  The 


HOUSEHOLD   CHEMISTRY  155 

presence  of  both  is  easily  shown  by  simple  processes.  If 
fresh  bones  be  steeped  for  several  days  in  10  per  cent, 
hydrochloric  acid,  the  mineral  matter  will  be  removed 
and  a  shrunken  but  flexible  cast  will  remain.  On  the 
other  hand,  the  mineral  matter  of  bone  will  persist  after 
long  careful  heating  in  its  original  shape.  The  same 
result  is  accomplished  much  more  slowly  by  weathering. 
The  food  material  in  bone  may  be  extracted  as  follows : 
Procure  raw  shin  bones  of  beef  and  have  them  well 
scraped  and  sawed  into  r-inch  sections.  Treat  these 
sections  for  2  or  3  hours,  under  slight  pressure,  in  a 
soup  digester  with  the  least  possible  amount  of  water. 
Pass  the  extract  through  cheese-cloth,  filter  into  a  tall 
glass  cylinder,  and  when  thoroughly  cool,  remove  the 
layer  of  fat  and  compare  with  tallow. 

Make  tests  for  protein  (biuret),  and  gelatin  on  the 
balance  of  the  extract. 

MUSCLE. 

The  muscle  mass  consists  of  a  series  of  elongated 
tubular  sacks  of  yellow  connective  tissue  (elastin)  ar- 
ranged in  bundles  and  held  together  by  white  connective 
tissue  (collagen).  Interspersed  in  the  mass  are  fat  glo- 
bules. 

Principal  Constituents  of  Muscle. — Proteins. — The  total 
proteins  of  the  muscle  mass  include  serum  albumin,  serum 
globulin,  haemoglobin,  elastin,  collagen,  and  especially 
paramyosinogen  and  myosinogen.  These  latter  yield 
myosin  on  a  clotting,  as  shown  on  next  page : 


156  HOUSEHOLD   CHEMISTRY 

paramyosinogen         myosinogen 

I 
soluble  myosin 

\    / 

myosin 
(clot) 

The  clotting  action  takes  place  at  death.  The  globulin- 
like  myosin  is  in  turn  gradually  softened  by  acids  set  free 
by  bacterial  action  (putrefaction)  during  "hanging". 

Carbohydrate. — Glycogen  and  glucose  are  generally 
present  in  muscle.  They  furnish  energy  for  muscle  con- 
traction, yielding  sarcolactic  acid  as  one  of  the  products 
of  fatigue.  Fresh  muscle  usually  contains  glycogen,  but 
on  standing  this  is  rapidly  changed  to  bacterial  lactic  acid. 

Extractives. — These  are  certain  nitrogenous  non-pro- 
tein bodies,  principally  creatin  and  creatinin.  They  give 
flavor  to  muscle,  and  being  readily  soluble,  are  found  in 
meat  extracts  and  soups. 

Mineral  Salts. — Principally  potassium  phosphate,  also 
chlorides  and  other  compounds  of  Ca,  Fe,  Na  and  Mg, 
including  a  trace  of  sulphates. 

EXPERIMENTS  ON  MUSCLE. 

Cut  off  the  exterior  of  a  piece  of  lean  meat,  test  the  interior 
with  litmus  paper  and  note  the  reaction.  Then  cut  the  meat  in 
small  pieces,  pass  through  a  meat  chopper  and  grind  the  result- 
ing mass  in  a  mortar  with  clean,  dry  sand.  Take  one-half  of 
the  ground  mass  and  extract  in  a  beaker  of  cold  water,  stirring 
every  few  minutes.  Allow  the  extraction  to  proceed  for  l/2  hour. 
Finally  filter  off  a  part  of  the  watery  extract  and  test  separate 
portions  as  follows : 


HOUSEHOLD   CHEMISTRY  157 

1.  Biuret. 

2.  Heat  over  water.    At  what  point  does  coagulation  begin? 

3.  Add  crystals  of  ammonium  sulphate  to   saturation;   filter, 
and  test  precipitate  and  filtrate  with  biuret. 

4.  Determine  whether  glycogen  is  present  as   follows :     Boil 
with   a   few   drops   of   hydrochloric   acid,   neutralize,   test   with 
Fehling's. 

Heat  the  remainder  of  the  water  extract  to  coagulate  the 
protein  and  filter.  To  the  filtrate  add  a  few  drops  of  HNO» 
and  burn  to  ash.  Cool,  take  up  with  water,  and  if  cloudy,  filter. 
Divide  into  five  parts  and  test  for  chlorides,  sulphates,  phos- 
phates, calcium  and  iron. 

Take  the  second  portion  of  the  ground  meat,  wash  it  free  from 
blood,  and  extract  it  with  three  or  four  times  its  bulk  of  10 
per  cent,  sodium  chloride,  allowing  it  to  stand  24  to  48  hours. 
Finally  filter  off  the  protein  solution  and  test  portions  as  follows : 

1.  Try  reaction  with  litmus. 

2.  Pour  a  few  drops  into  a  large  excess  of  water.    Note  milky 
precipitate  of  myosin. 

3.  Heat  to  coagulating  point ;  what  is  it  ?    Is  the  litmus  reaction 
the  same  after  heating? 

4.  Saturate  with  salt,  shaking  vigorously.    What  effect  on  the 
myosin?    Filter.    Dissolve  precipitate  in  10  per  cent.  NaCl  and 
make  biuret  test  on  solution. 

From  the  composition  of  muscle  and  the  tests  made 
deduce  the  effect  on  meat  of  washing,  placing  in  dilute 
salt  solution,  corning,  soup  making,  and  roasting. 

BEEF  EXTRACTS. 

Composition. — The  food  value  of  these  extracts  is 
slight,  and  their  function  is  to  serve  as  stimulants  or 
appetizers,  and  flavoring  material.  Commercial  extracts 


158  HOUSEHOLD   CHEMISTRY 

contain  little  if  any  protein  material,  since  such  proteins 
as  may  be  extracted  are  coagulated  by  heat  and  removed 
by  filtration.  Home-made  extracts  and  clear  soups  lose 
food  value  by  clarifying.  No  fats  or  carbohydrates  are 
found  in  the  average  market  extract;  the  principal  in- 
gredients are  extractives  and  the  mineral  salts  of  muscle. 

TESTS  ON  HOME-MADE  AND  COMMERCIAL 
EXTRACTS. 

Make  meat  extract  by  steeping  lean  meat  in  cold  salt  water, 
gradually  heating  to  a  boil  and  finally  under  slight  pressure. 
Pour  off  the  liquid,  cool,  remove  the  fat,  dissolve  some  of  the 
jelly  in  warm  water  and  compare  with  Leibig's  and  other  meat 
extracts  made  on  the  commercial  scale,  by  the  following  tests  : 

1.  Biuret. 

2.  Glycogen  test  (Iodine). 

3.  Creatinin  (Weyl's  Test).  —  Add  a  few  drops  of  a  5  per  cent. 
solution  of  sodium  nitroprusside,  freshly  prepared,  and  cautiously 
38°  Baume  NaOH.    A  ruby  red  changing  to  straw  color  shows 
creatinin. 

4.  Examine  the  solid  extract  under  the  microscope  and  note 
the  cubical  crystals  of  salt  and  knife-rest  forms  of  creatinin. 

5.  Clarify  beef  extract  with  white  of  egg,  filter  and  test  filtrate 
for   protein   with  biuret.     Compare   with   test   on   beef   extract 
before  clarifying. 


This  term  usually  refers  to  cow's  milk  in  market  form. 
Analyses  show  that  the  composition  of  milk  varies  with 
different  breeds  of  cows,  the  principal  variation  being  in 
the  fat  content.  Approximate  averages  are  as  follows.* 

*  For  detailed  composition    of    milk,    see   Sherman's  Food 
Products. 


HOUSEHOLD    CHEMISTRY 


159 


Per  cent. 

Per  cent. 

Water  

87.2 
12.8 
3-6 
3-3 
4-9 
0.7 

87.0 
13.0 

40 
3-3 
5-o 
o.7 

Total  solids  

fat    

In  most  states,  the  amount  of  fat  in  milk  offered  for 
sale  is  regulated  by  law.  The  New  York  State  Standard 
requires  at  least  3  per  cent.  fat. 

The  Fats. — The  true  fats  in  milk  are  glycerides  of  both 
volatile  and  non-volatile  fatty  acids.  Of  the  former, 
butyrin  is  the  most  important,  forming  5  to  7  per  cent 
of  the  fat  content.  When  hydrolyzed,  its  free  butyric 
acid  gives  a  taste  and  odor  to  rancid  butter.  The  prin- 
cipal fats  of  the  non-volatile  acids  are  palmitin  in  large 
amount,  stearin,  and  olein.  In  freshly  drawn  milk  tiny 
globules  of  fat  are  held  in  suspension  by  the  mixed  pro- 
teins present,  but  on  standing  the  emulsion  breaks,  and 
the  cream  separates  more  or  less  completely.  However, 
it  is  not  until  the  emulsifying  power  of  the  protein  is  de- 
stroyed by  the  action  of  lactic  acid  developed  in  souring, 
that  the  fat  particles  run  together  and  are  combined  in 
the  form  of  butter  by  churning. 

Proteins. — The  protein  constituents  of  milk  are  prin- 
cipally caiseinogen,  with  small  amounts  of  albumin,  glo*- 
bulin,  and  fibrinogen.  Caseinogen  is  strongly  acid  in 
character,  is  insoluble  in  water,  but  is  held  in  solution 


l6o  HOUSEHOLD   CHEMISTRY 

as  a  calcium-caseinogenate  by  the  lime  phosphates  in  the 
milk. 

Carbohydrate. — Lactose  is  the  main  form  of  carbohy- 
drate material.  In  amount  it  shows  less  variation  than 
any  other  ingredient  except  mineral  salts. 

Ash  Constituents. — The  principal  ash  constituents  are 
in  the  form  of  lime  phosphates,  found  either  combined 
with  protein  or  other  organic  material,  such  as  lecithin,  or 
free  as  mineral  salts.  Combined  citric  acid  is  present  in 
small  amount,  also  chlorides  and  other  salts  of  Na,  K  and 
Mg.  Iron  and  sulphur  are  found. 

Other  Constituents. — Urea,  creatinin,  lecithin,  choles- 
terol and  hypoxanthine  are  present  in  varying  amounts; 
also  a  color  substance,  carbohydrate-  and  fat-splitting 
enzymes,  an  oxydase,  a  reductase,  and  a  catalase. 

Fresh  milk  has  an  amphoteric  reaction  to  litmus,  due 
to  the  fact  that  it  has  two  classes  of  phosphates  in  solu- 
tion. Its  specific  gravity  varies  from  1.029  to  1.035. 

Effect  of  Heating. — Under  the  conditions  usually  em- 
ployed for  pasteurization  (145°  F.  for  i  hour)  few 
if  any  chemical  changes  are  produced  in  milk — the  object 
being  to  destroy  certain  pathogenic  bacteria.  Boiling 
milk  produces  both  physical  and  chemical  changes,  some 
of  which  are  the  alteration  in  the  physical  state  of  the 
fat  globules,  a  tendency  to  precipitation  of  the  lime  salts, 
the  destruction  of  most  organisms,  and  the  appearance  of 
total  solids  in  the  skin  which  forms  after  boiling.  This 
formation  is  not,  as  sometimes  explained,  coagulated  pro- 
tein material,  but  is  due  to  the  concentration  of  total 
solids  as  the  water  evaporates. 


HOUSEHOLD   CHEMISTRY  l6l 

Souring  of  Milk. — By  the  activities  of  lactic  acid 
bacteria  lactose  is  decomposed  into  lactic  acid : 

C..H.A,,  H20  —  4C3H60S. 

Other  fermentation  products  may  also  be  formed,  such 
as  acetic,  propionic  or  butyric  acid,  and  some  alcohol, 
e.g.: 

4CSH603  —  2C4H802  +  4CO,  +  4Ha. 

lactic  acid  butyric  acid 

When  the  lactic  acid  reaches  approximately  0.5  per 
cent.,  caseinogen  begins  to  be  precipitated ;  the  extreme 
amount  of  lactic  acid  developed  is  generally  about  0.9 
per  cent.  The  action  of  acids  on  caseinogen  has  been 
described  under  Curdling  (p.  I46)  but  the  changes  taking 
place  in  this  case  may  possibly  be  represented  by  the 
expression : 

(lactic  acid) 

Ca-caseinogenate       •>-*       caseinogen 

(soluble)  (insoluble) 

-f-  acid  Ca-phosphate. 

When  baking  soda  is  used  with  sour  milk  the  acid 
caseinogen  combines  with  the  alkaline  carbonate,  form- 
ing sodium  caseinogenate,  carbon  dioxide  and  water. 

Action  of  Rennin. — The  clotting  action  of  rennin  has 
been  referred  to  under  Clotting  (p.  I46).  Conditions  for 
the  best  action  of  the  enzyme  are  brought  out  in  experi- 
ments on  p.  165. 

Fermentation  with  Yeast. — Milk  does  not  readily  un- 
dergo fermentation  with  ordinary  yeast  unless  some  food 
for  the  yeast  is  added.  For  kephir  or  koumiss  a  special 


1 62  HOUSEHOLD   CHEMISTRY 

yeast  ferment  is  used,  which  changes  the  lactose  into 
alcohol,  lactic  acid,  and  various  other  acid  fermentation 

products. 

TESTS  ON  MILK. 

Physical — i.  Cream  Gauge. — Fill  to  mark  with  freshly  mixed 
milk.  Allow  the  tube  and  contents  to  rest  quietly  for  half  an 
hour  and  read  off  percentage  of  top  milk  from  graduated  scale. 

2.  Lactometer. — Fill  a  tall  jar  with  freshly  mixed  milk,  tem- 
perature 60°  F.    Immerse  the  instrument  and  when  it  comes  to 
rest  read  off  the  percentage  of  purity  on  the  scale.    On  the  New 
York  Board  of  Health  lactometer  the  zero  mark  records  a  specific 
gravity  of  i.ooo  and  the  100  mark  a  specific  gravity  of  1.029.    In 
similar  manner,  determine  the  purity  of  skim  milk.    Finally,  add 
water  and   redetermine  the   purity;   how   can   you   explain   the 
result  ? 

3.  Pioscope  Test. — Depends  on  opacity.     Place  a  drop  or  two 
of  freshly  mixed  milk  in  the  center  of  the  hard  rubber  disc. 
Cover   carefully   with   the   glass    plate   and   compare    with    the 
standard  scale  of  colors. 

4.  Lactoscope  Test.— Use  Feser's  lactoscope.     Fill  the  pipette 
with  milk,  allow  it  to  run  into  the  cylinder.     Cautiously  add 
water,  shaking  after  each  addition,  until  the  marks  on  the  cloudy 
glass   rod  are   just  visible   through   the   liquid.     Read   off   and 
record  the  percentage  of  fat  at  the  level  of  the  liquid. 

5.  Microscope  Test. — Examine  a  drop  of  milk  under  the  micro- 
scope ;  add  a  drop  of  10  per  cent,  caustic  soda  and  re-examine. 
What  is  the  result  ? 

Chemical  Tests. — i.  Using  fresh  milk,  what  is  the  reaction  with 
delicate  litmus  paper? 

2;  Babcock  Test  (Determination  of  Fat). — This  test  depends 
on  the  decomposition  of  the  organic  constituents,  with  the  excep- 
tion of  the  fats,  which  are  at  the  same  time  set  free  in  the  liquid 
state  and  may  be  measured. 

Fill  the  milk  pipette  (17.6  cc.)  with  freshly  mixed  milk,  dis- 
charging the  contents  into  the  Babcock  bottle,  add  an  equal 


HOUSEHOLD   CHEMISTRY  163 

volume  of  oil  of  vitriol  (specific  gravity  1.8).  Mix  by  revolving 
the  bottle  gently  in  a  small  arc,  back  and  forth,  until  the  residue 
disappears  and  the  mass  is  brown  in  color.  Make  tests  up  in 
duplicate  and  whirl  them  for  5  minutes  in  the  centrifuge  over 
hot  water.  Stop  the  machine,  add  enough  warm  water  to  bring 
liquid  level  half  way  up  the  graduated  neck  of  bottle.  Replace 
them  in  centrifuge  and  whirl  3  minutes,  allowing  machine  to  run 
down.  Take  out  bottle  and  read  per  cent,  of  clear  yellow  fat 
floating  on  the  water. 

3.  Separation  and  Identification  of  Caseinogen. — Dilute  10  cc. 
of  fresh  raw  milk  with  water  up  to  about  100  cc.,  add  slowly 
the  least  quantity  (6-8  cc.)  of  2  per  cent,  acetic  acid  required  to 
precipitate  the  caseinogen,  warming  meanwhile  to  60°,  filter 
through  moist  fluted  paper  and  reserve  the  clear  filtrate  for 
test  B.  Operate  with  the  residue  as  follows : 

A.  Residue  of  Caseinogen.  Wash  several  times  with  the  same 
amount  of  hot  95  per  cent,  alcohol,  evaporate  the  alcohol  extract 
over  hot  water,  notice  the  appearance  of  the  oily  substance 
remaining,  and  make  a  fat  test  upon  it.  Remove  excess  of  liquid 
from  the  caseinogen  residue  by  pressing  between  dry  filter  paper, 
and  spread  out  to  dry.  Dissolve  a  portion  in  about  25  cc.  of 
warm  5  per  cent,  salt  solution,  slightly  acidified  with  acetic  acid. 
Stand  in  hot  water  for  some  minutes  and  filter.  Add  a  few 
drops  of  the  clear  filtrate  to  a  saturated  solution  of  salt,  adding 
dry  salt  if  necessary.  What  are  the  solubilities  of  caseinogen 
in  salt  solutions?  Make  nitric  acid  and  biuret  tests  on  portions 
of  the  dissolved  caseinogen.  Add  another  considerable  portion 
of  the  clear  filtrate  to  ammonium  oxalate,  made  strongly  alka- 
line with  NH.iOH.  Heat  and  observe  white  crystalline  precipi- 
tate of  calcium  oxalate.  Fuse  the  remaining  portion  of  dried 
caseinogen  with  sodium  nitrate  in  a  porcelain  crucible,  cool,  and 
extract  the  contents  of  the  crucible  with  diluted  HNOs  (1:5). 
Filter,  and  add  a  few  drops  of  the  clear  liquid  to  (NHOaMoCX 
solution.  Warm  and  observe  yellow  crystalline  precipitate,  indi- 
cating presence  of  phosphoric  acid. 


164  HOUSEHOLD   CHEMISTRY 

B.  Divide  the  whey  filtrate   (reserved)   into  three  equal  por- 
tions. 

i.Heat  in  boiling  water  and  observe  the  clouding  (lactalbumin). 
Filter,  test  precipitate  for  protein,  and  filtrate  for  lactose  with 
Fehling's  reagent. 

2.  Add    potassium    ferrocyanide    and    excess    of    acetic   acid. 
Observe  the  precipitate  of  lactalbumin. 

3.  Heat  in  boiling  water,  filter  off  lactalbumin,  boil  the  filtrate 
and  observe  the  precipitate,  principally  insoluble  calcium  citrate. 
Reserve  filtrate. 

NOTE. — If  milk  has  been  thoroughly  pasteurized,  it  will  not 
respond  to  the  tests  for  lactalbumin. 

C.  Evaporate  the  filtrate,  from  last  test,  to  dryness;  ignite  in 
the  presence  of  a  few  drops  of  HNO3,  cool,  dilute  with  water 
and  test  for  chlorides,  sulphates  and  phosphates. 

Analysis  of  Milk — Measure  5  cc.  of  milk  with  a  pipette,  trans- 
fer it  to  a  weighed  shallow  porcelain  dish  and  weigh  again. 
Difference  is  weight  of  milk.  Place  over  hot  water  (kept  just 
below  the  boiling-point)  to  evaporate  water  present  in  milk. 
Cool  and  weigh ;  loss  is  water,  residue  is  total  solids.  Total 
solids  should  be  12-13  per  cent.  To  extract  fat,  add  about  10  cc. 
of  ether  to  contents  of  dish,  heat  over  warm  water  i  or  2  min- 
utes, decant  solution  into  a  second  weighed  dish.  Repeat  the 
ether  treatment  three  times.  When  dry,  weigh  original  dish ; 
the  loss  is  fat.  Evaporate  ether  from  second  dish,  weigh ;  the 
gain  is  fat  and  should  check  the  loss. 

To  extract  lactose  and  soluble  salts,  treat  contents  of  dish 
with  warm  water.  Allow  it  to  stand  for  several  minutes,  decant 
the  liquid;  repeat  the  operation  three  times.  Dry  the  dish  and 
weigh ;  loss  is  lactose  and  half  the  mineral  salts  found  in  milk. 

Ignite  the  contents  of  dish  to  a  gray  ash ;  protein  matter  will 
burn  off.  Cool  and  weigh;  the  loss  is  protein,  residue  is  insol- 
uble salts.  Assuming  that  insoluble  salts  are  one-half  of  the 
total  salts,  double  the  figure  obtained.  To  determine  amount  of 
lactose,  subtract  one-half  of  total  salts  from  the  figure  obtained 


HOUSEHOLD   CHEMISTRY  165 

on  lactose  and  soluble  salts.     The  difference  is  the  amount  of 
lactose. 

Determination  of  Lactose — Into  a  glass  stoppered  cylinder,  put 
100  cc.  milk  and  2  cc.  Millon's  reagent.  Mix  thoroughly  and 
pour  into  a  beaker  placed  over  hot  water.  Allow  the  mixture  to 
stand  until  all  protein  matter  has  precipitated,  filter  off  the  clear 
whey  through  moist  fluted  paper.  Make  it  alkaline  with  dry 
sodium  carbonate,  adding  a  little  at  a  time  until  pink  litmus  paper 
turns  blue.  If  cloudy  filter  again.  Pour  into  a  burette  and  deal 
with  it  as  with  sugar.  Calculate  that  0.068  gram  will  reduce 
10  cc.  Fehling's  reagent. 

Effect  of  Rennet. — In  the  following  experiments  with  rennet, 
make  the  tests  comparative  by  using  the  same  amount  of  milk 
and  rennet  solution  throughout,  e.g.,  10  drops  of  liquid  rennet 
to  30  cc.  of  milk  in  each  case. 

1.  Heat  milk  to  the  boiling-point,  boil  gently  for  5  minutes, 
replacing   any   liquid    lost    during   evaporation    by    hot    distilled 
water,  cool  to  40°  and  add  rennet ;  note  the  character  and  amount 
of  clot. 

2.  Boil  milk  15-20  minutes,  keeping  the  liquid  up  to  bulk  as 
before;  cool  to  40°,  add  rennet;  note  character  and  amount  of 
clot. 

3.  To  the  sample  of  milk,  add  1-2  cc.  of  ammonium  oxalate 
solution  (precipitant  for  lime),  boil  for  2-3  minutes,  cool  to  40° 
and  add   rennet;   note   character   and  amount  of   clot,   if   any. 
Finally  add  limewater  equal  in  bulk  to  the  original  milk,  warm 
to  40°  and  note  the  result. 

4.  Repeat  the  above,  adding  I  cc.  of  a  diulte  solution  of  cal- 
cium acid  phosphate,  instead  of  limewater. 

5.  Add  i  cc.  of  0.2  per  cent.  HC1  to  the  milk  and  test  with 
rennet  at  40°.     Does  a  clot  form?     Repeat,  using  i  cc.  of   10 
per  cent.  Na2CO3.    What  is  the  effect  of  alkali  on  rennet  action? 

6.  Note   the   effect   of   rennet   on   separate   portions   of   milk 
heated  to  30°,  40°,  50°,  80°.    Tabulate  the  results  of  the  above 
tests. 


l66  HOUSEHOLD   CHEMISTRY 

Butter-Fats. — Half  fill  two  small  flasks  (50  cc.),  one  with  pure 
and  the  other  with  skim  milk.  Add  to  each  half  a  volume  of 
ether  and  a  few  drops  of  caustic  soda,  cork  and  rotate  well. 
Uncork  and  place  in  a  beaker  of  warm  water  and  allow  them  to 
remain  quiet.  In  a  few  minutes,  note  the  layer  of  oil  and  ether 
floating  on  the  surface.  Remove  some  of  the  ether  layer  from 
each  with  a  pipette  and  evaporate  at  a  low  heat.  Note  the 
differences  in  amount  of  the  butter  residue. 

Souring. — i.  Place  some  milk  in  a  wide-mouthed  bottle,  allow 
it  to  stand  in  a  warm  place  for  some  days  or  until  sour.  Finally 
filter  off  the  curd  and  test  the  filtrate  for  lactose  and  for  acidity 
by  titrating  with  lo/N  alkali,  calculating  to  lactic  acid.  What 
weight  of  bicarbonate  of  soda  would  neutralize  the  amount  of 
acid  found? 

2.  Measure  standard  cupfuls  of  slightly  sour,  moderately 
sour,  and  very  sour  milk.  Weigh  the  amount  of  baking  soda 
required  to  fill  a  standard  teaspoon  and  add  the  soda  in  small 
amounts  to  the  milk  sample,  mixing  thoroughly  after  each 
addition,  and  testing  with  litmus  paper.  Determine  the  weight 
of  soda  required  to  neutralize  the  acidity  in  each  of  the  three 
samples  of  milk,  and  express  the  amount  in  fractional  parts  of 
a  teaspoon. 

Condensed  or  Evaporated  Milks  should  be  diluted  with  distilled 
water  to  the  original  bulk  and  treated  as  normal  milks.  The 
index  of  condensation  may  be  estimated  by  observing  the  rela- 
tive amount  of  dilution  necessary. 

Preserved  milks  commonly  contain  cane  sugar.  Dilute  a 
sample  to  the  original  bulk,  precipitate  the  caseinogen  with  dilute 
acetic  acid;  filter  and  exactly  neutralize  the  filtrate  with  sodium 
carbonate  and  test  for  sucrose  with  cobalt  chloride  and  caustic 
soda. 

Formalin  in  Milk. — Add  i  drop  of  ferric  chloride  solution  to 
50  cc.  of  concentrated  H2SO4.  Pour  5  cc.  of  the  mixture  down 
the  side  of  a  test  tube  containing  20  cc.  of  the  milk  under  test. 
If  formalin  is  present,  a  violet  band  will  appear  at  the  contact 
point  of  the  two  liquids. 


HOUSEHOLD   CHEMISTRY  167 

Analysis  of  Ice  Cream — For  Gelatin. — Dilute  50  parts  of  ice 
cream  with  25  parts  of  water  and  bring  to  the  boiling  point,  to 
dissolve  any  thickener  other  than  gelatin  that  may  be  present 
and  not  in  complete  solution.  To  10  cc.  of  the  product  add  an 
equal  amount  of  acid  nitrate  of  mercury  solution1  and  about 
20  cc.  of  cold  water.  Shake  vigorously,  allow  to  stand  5  min- 
utes, then  filter.  If  much  gelatin  is  present  the  filtrate  will  be 
opalescent  and  cannot  be  obtained  clear.  To  a  portion  of  the 
filtrate  add  an  equal  volume  of  a  saturated  solution  of  picric 
acid.  A  yellow  precipitate  will  indicate  gelatin  in  any  consid- 
erable amount;  smaller  amounts  are  shown  by  a  cloudiness.  In 
the  absence  of  gelatin  the  filtrate  obtained  will  remain  quite 
clear. 

For  Fat. — Make  estimation  as  soon  as  possible  after  sample 
has  melted.  Weigh  9  grams  of  the  sample  in  a  Babcock  cream 
bottle.  Add  30  cc.  of  a  mixture  of  equal  parts  by  volume  of 
concentrated  HC1  and  80  per  cent.  CH3COOH.  Heat  on  a  water 
bath  until  well  darkened,  but  short  of  charring.  Whirl  in  a 
Babcock  centrifuge  and  read  the  percentage  of  fat  directly.  If 
the  cream  is  charred,  add  ether  after  the  whirling,  draw  off  the 
layer  containing  the  fat  into  another  Babcock  bottle,  evaporate 
the  ether,  fill  the  bottle  with  water,  and  again  read  percentage 
of  fat  after  whirling. 

Character  of  Fatty  Matter. — For  observing  the  char- 
acter of  the  fat,  30-40  cc.  of  the  cream  layer  are  placed 
in  a  Babcock  cream  bottle,  i  cc.  of  strong  mercuric 
nitrate  solution  and  20  cc.  of  petroleum  ether  are  added, 
and  after  whirling,  the  ethereal  layer  is  separated,  washed 
with  water,  and  the  ether  evaporated. 

\j  J^  Pi  Fi^.  Kl  T 

A  product  prepared  from  the  caseinogen  of  milk  with 
or  without  the  fat.     The  milk  is  clotted  with  rennet,  sepa- 
1  Jour.  Amer.  Chent.  Soc.,  1907. 


l68  HOUSEHOLD   CHEMISTRY 

rated  from  the  whey,  ground,  salted,  pressed  into  shape 
and  cured.  The  curing  operation  consists  in  subjecting 
the  cheese  mass  to  the  action  of  certain  bacteria  and 
moulds,  which  form  acids,  hydrolyze  the  proteins  and 
develop  flavor  and  odor. 

Cottage  cheese  is  merely  finely  divided  caseinogen  pre- 
cipitated by  the  lactic  acid  of  the  souring  process  aided 
by  the  heating  and  undergoes  no  further  change. 

Cheeses  are  usually  made  from  cow's  milk  but  may  be 
produced  from  goat's  or  ewe's  milk  or  mixtures  of  all 
of  them.* 

EXPERIMENTS  ON  CHEESE. 

Take  a  sample  of  well-cured  cheese,  grind  some  of  it  in  warm 
5  per  cent.  NaCl  solution,  filter  and  reserve  the  residue. 
Divide  the  filtrate  into  four  parts  and  test  as  follows : 

1.  For  acidity  or  alkalinity  with  litmus  paper  and  N/io  acid 
or  alkali. 

2.  For  state  of  protein  matter,  by  biuret  test. 

3.  For  soluble  mineral  matter,  ».  e.,  sulphates,  etc. 

4.  For  ammonia  and  sulphides. 

Extract  the  residue  several  times  with  the  same  portion  of  hot 
neutral  alcohol,  cool,  and  test  the  extract  with  litmus  paper  for 
fatty  acids.  When  cold,  observe  the  cloudy  precipitate  of  esters. 
Separate  by  filtration  and  test  for  free  fatty  acid  and  fats. 

Divide  the  extracted  residue  into  two  parts  and  test  as  follows : 

1.  For  insoluble  protein. 

2.  Burn  to  white  ash  and  test  for  insoluble  mineral  matter — 
phosphates,  lime,  etc. 

During  the  incineration,  hold  pieces  of  moistened  red  litmus 
and  lead  acetate  papers  in  the  fumes  and  record  the  results. 

*  For  further  information,   see  Vulte*   and   Vanderbilt,  Food 
Industries,  and  Wing,  Milk  and  Milk  Products. 


HOUSEHOLD   CHEMISTRY  169 

Cheeses  are  frequently  preserved  in  wrappings  saturated  with 
borax  or  boracic  acid  solution.  To  determine  this,  steep  some 
of  the  paper  wrapping  in  warm  water,  filter  if  necessary,  acidify 
with  HC1  and  dip  pieces  of  turmeric  paper  in  the  liquid.  Dry 
these  at  212°  F. ;  a  pink  color  indicates  borates. 


CHAPTER  XL 


BAKING  POWDERS. 

It  is  frequently  necessary  to  develop  carbon  dioxide 
for  leavening  purposes  more  rapidly  than  by  the  agency 
of  yeast.  For  this  purpose  the  purely  chemical  method 
by  the  acid  decomposition  of  carbonates  or  bicarbonates 
is  most  available. 

Undoubtedly  the  time-honored  custom  of  using  salera- 
tus  (bicarbonate  of  potash)  and  sour  milk  (lactic  acid) 
furnished  the  original  idea  on  which  the  modern  mix- 
tures were  built  up.  This  original  idea  still  survives  to 
some  extent  in  modern  practice,  but  is  open  to  at  least 
two  strong  objections.  First,  bicarbonate  of  potash  is  no 
longer  a  commercial  article  but  is  replaced  by  the  cheaper 
and  stronger  bicarbonate  of  soda ;  still  no  change  is  made 
in  the  proportions  used.  Second,  it  is  very  difficult  to 
estimate  the  amount  of  lactic  acid  in  sour  milk  by  simple 
means  with  any  accuracy.  In  fact  the  quantity  is  usually 
largely  over-estimated.  When  milk  shows  decided  in- 
dications of  the  sour  stage  only  4/10  of  one  per  cent,  of 
lactic  acid  are  usually  found.  It  must  be  remembered 
that  any  excess  of  the  bicarbonate  used  is  changed  into 
alkaline  normal  carbonate  by  the  heat  of  baking. 

For  the  above  stated  reasons  it  can  easily  be  seen  that 
accurately  compounded  mixtures  (leaving  neither  alka- 
line nor  acid  residues),  retaining  their  qualities  for 
some  time  in  the  dry  state,  but  ready  to  develop  gas  on 
addition  of  water,  have  a  decided  advantage.  In  order  to 
preserve  these  mixtures  in  a  dry  state,  it  has  been  found 


HOUSEHOLD   CHEMISTRY  171 

advisable  to  add  to  them  such  agents  as  raw  starch  and 
pulverized  lactose,  which  are  perfectly  harmless.  Such 
additions  should  not  in  any  case  exceed  25  per  cent,  of 
the  whole  mass.  When  used  for  this  purpose  the  com- 
pounds are  known  as  "fillers." 

Modern  baking  powders  may  be  classed  as  tartrate, 
phosphate,  and  alum  phosphate.  All  contain  bicarbonate 
of  soda,  while  the  acting  acid  ingredient  varies,  as 
follows : 

Tartrate — Cream  of  tartar,  KHC4H4O6,  and  sometimes 
a  small  amount  of  free  tartaric  acid,  H2C4H4O6. 

Phosphate — Soluble  phosphate  of  lime,  CaH4(PO4)2. 

Alum  phosphate,  same  as  above  with  addition  of  dry 
alum,  K2,  Na2,  or  (NH4)2,  A12(SO4)4." 

The  following  reactions  clearly  show  the  changes  tak- 
ing place  in  using  these  mixtures : 

For  tartrates: 
KHC4H4O6  +  NaHCO3  +  3H2O  — 

188  84  54 

KNaC4H4O6)  4H2O  +  CO2. 

282  44 

For  phosphates: 
CaH4(PO4)a  -f  2NaHCO,  -f  ioHaO  — 

234  168  180 

CaHPO4  -f-  Na,HPO4,  I2H2O  -f  2CO2. 

136  358  88 

For  alum  phosphates: 
(NH4)2A12(SO4)4+  CaH4(PO4),  +  4NaHCO8  +  8H,O  — 

475  »34  S3*  144 

A12(PO4),  +  CaSO4  2H2O  +  (NH4),SO4  -f 

245  192  182 

2Na2SO4ioH2O  -f  4 

644 

12 


\J2  HOUSEHOLD   CHEMISTRY 

It  is  significant  that  the  tartrate  powders  leave  no  in- 
soluble residue  except  starch,  while  the  others  leave 
nearly  one-third  of  their  weight  in  insoluble  mineral  mat- 
ter besides  the  starch.  The  phosphates  yield  the  acid 
soluble  phosphate  of  lime,  of  doubtful  utility,  and  the 
alum  powders,  alumina  phosphate  and  calcium  sulphate. 

The  table  of  comparison  on  p.  173  is  taken  from  Vulte 
and  Vanderbilt's  Pood  Industries. 

An  efficient  baking  powder  can  be  made  at  home  at  a 
low  cost  by  combining  the  following  ingredients : 
l/2  pound  cream  of  tartar. 
y$  pound  baking  soda. 
l/4  pound  cornstarch. 

For  maximum  efficiency  these  suggestions  should  be  ob- 
served: Dry  the  cornstarch  before  combining;  mix  and 
sift  the  ingredients  thoroughly;  either  make  up  small 
quantities  or  pack  in  small  tightly  closed  receptacles. 

Ammonium  carbonate  is  sometimes  used  as  a  baking 
powder,  since  it  yields  carbon  dioxide  when  heated : 
(NH4)2CO,  —  NH,  +  CO,  -f  H2O. 

It  will  be  seen  that  all  the  products  are  volatile,  no 
residue  being  left  unless  an  excess  of  the  powder  is  used. 
In  that  case  an  unpleasant  taste  is  noticed  in  the  product. 
The  amount  of  powder  required  is  only  about  one-tenth 
as  much  as  of  other  powders. 

EXPERIMENTS. 

Tartrates — Mixtures  of  cream  of  tartar  and  bicarbonate  of 
soda  with  starch  or  lactose  filler.  Treat  a  small  portion  of  the 
powder  with  water  and  after  the  effervescence  has  ceased  test 
a  portion  of  the  liquid  for  starch  with  iodine  solution  and  for 


HOUSEHOLD    CHEMISTRY 


173 


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174  HOUSEHOLD   CHEMISTRY 

lactose  with  Fehling's  solution,  boil  the  remainder  of  the  liquid, 
cool,  filter  through  fluted  paper,  and  test  with  litmus  paper. 

1.  Place  a  few  drops  of  the  clear  liquid  on  a  slide  and  allow 
it  to  evaporate  spontaneously.     Examine  the  cleft  rectangular 
crystals  of  Rochelle  salt. 

2.  Fenton's  Test. — Test  another  portion  of  the  solution  by  add- 
ing  I   drop  of   fresh  cold  dilute  solution  of   ferrous   sulphate, 
I  or  2  drops  of  peroxide  of  hydrogen  and  immediately  a  large 
excess  of  38°  Baume  caustic  soda — a  violet  color  appears,  due  to 
tartrates.     Evaporate  the  balance  of  the  solution  in  a  porcelain 
dish,  char  and  gently  ignite  the  residue.     Note  the  odor  while 
carbonizing;  what  does  it  suggest?     Cool,  add  water  and  test 
with  litmus  paper ;  why  is  it  alkaline  ? 

Neutral  tartrates  will  respond  to  the  silver  mirror  test. 

Tartrate  powders  may  contain  a  small  amount  of  bicarbonate 
of  ammonia.  To  test  for  this,  heat  a  portion  of  the  powder  in 
a  test  tube  with  caustic  soda  solution ;  observe  the  odor ;  or  hold 
a  strip  of  moistened  red  litmus  paper  over  the  mouth  of  the 
tube. 

Phosphate  Powders — Calcium  hydrogen  phosphate,  bicarbonate 
of  soda  and  starch  filler.  Make  a  water  solution  and  test  for 
filler  as  in  the  case  of  tartrates.  Divide  the  remainder  of  the 
solution  into  three  parts. 

1.  Add  a  few  drops  of  the  liquid  to  an  excess  of  ammonium 
molybdate.     Heat  gently;  a  yellow  precipitate  indicates  phos- 
phates. 

2.  Add  ammonium   oxalate,   and   ammonium  hydroxide  until 
alkaline    and    boil — white    precipitate    indicates    calcium.     This 
should  give  a  yellowish  red  flame  on  platinum  wire. 

3.  As  these  powders  frequently  contain  alum  it  is  necessary  to 
make  a  test.    Probably  the  best  method  for  the  determination  of 
alum  is  to  add  a  portion  of  the  solution  to  tincture  of  logwood 
diluted  with  2  or  3  volumes  of  water,  finally  adding  an  equal 
volume  of  ammonium  carbonate.     In  the  presence  of  alum  the 
liquid  is  colored  lavender  or  dark  blue. 


HOUSEHOLD   CHEMISTRY  175 

Carbon  Dioxide  Determination  by  the  Scheibler  Apparatus. — 
Weigh  out  500  milligrams  of  the  baking  powder,  place  in  the 
glass-stoppered  bottle  belonging  to  the  apparatus.  Put  a  small 
quantity  of  water  in  the  gutta  percha  tube  (two-thirds  full). 
The  columns  of  water  in  the  apparatus  will  be  at  the  same  level 
when  the  pressure  inside  of  the  apparatus  is  the  same  as  the 
atmospheric  pressure,  and  this  should  be  the  condition  when 
the  experiment  is  started.  The  gutta  percha  tube  is  placed  inside 
the  bottle  containing  the  500  milligrams  of  baking  powder  and 
the  apparatus  is  then  connected  up.  Be  sure  the  relief  valve  is 
open  when  the  apparatus  is  put  together  and  closed  immediately 
afterwards.  Incline  the  generating  bottle  to  allow  the  water  to 
come  in  contact  with  the  powder.  Observe  the  evolution  of  gas. 
Note  the  height  of  the  watef  column.  Grasp  the  generating 
bottle  by  the  neck  and  shake  vigorously  until  no  more  gas  is 
evolved.  Immediately  afterwards  balance  the  water  columns  by 
allowing  some  water  to  escape  into  the  overflow  flask.  Read 
the  figure  nearest  the  level  of  the  water.  This  reading  indicates 
the  per  cent,  of  gas  liberated  by  the  addition  of  water  to  the 
baking  powder,  or  in  other  words,  the  leavening  power  of  the 
baking  powder.  This  reading  should  be  in  the  neighborhood  of 
10,  indicating  100  per  cent,  efficiency,  in  a  fresh  tartrate  powder. 


CHAPTER  XII. 


TEA,  COFFEE,  CHOCOLATE  AND  COCOA. 

Tea  consists  of  the  cured,  dried  and  rolled  leaves  of  a 
variety  of  plants  known  as  the  Thea.  According  to  the 
age  of  the  leaf  gathered,  there  are  four  well  known 
grades,  Pekoe  the  youngest,  Souchong  next,  Congou  next 
and  Bohea  the  oldest.  All  these  are  found  in  the  grades 
of  green  or  black  as  the  method  of  curing  varies.  Green 
teas  are  not  fermented,  black  teas  are  fermented,  and 
since  fermentation  tends  to  reduce  the  amount  of  tannin, 
the  latter  are  very  generally  preferred. 

The  principal  constituents  of  tea  are  the  alkaloid 
caffein,  tannin,  ash,  and  essential  oil.  As  a  rule  more 
caffein  is  found  in  black  teas  than  in  green,  and  more 
tannin  and  essential  oil  in  the  latter. 

A  proper  infusion  of  tea  is  made  by  steeping  the  leaves 
in  freshly  boiled  water  (preferably  slightly  hard)  just 
below  boiling.  Five  minutes  is  sufficient  to  make  the  ex- 
tract, when  it  will  contain  the  maximum  of  oil,  extract 
and  caffein  and  the  minimum  of  tannin.  It  should  now 
be  poured  off  the  leaves  and  used.  Boiling  or  long  stand- 
ing increases  the  amount  of  tannin  in  the  infusion,  while 
it  does  not  materially  affect  the  caffein  or  extract. 

EXPERIMENTS  ON  TEA. 

Make  an  infusion  according  to  rule  given  in  the  text,  pour  off 
the  clear  liquid,  filtering  if  necessary,  and  examine  the  leaves 
with  a  magnifier.  Add  a  few  drops  of  the  clear  filtrate  to  a 
weak  starch  solution  faintly  colored  with  iodine;  if  tannin  is 
present  the  color  will  fade.  Determine  caffein  in  the  balance  of 
the  extract  as  follows :  Add  basic  acetate  of  lead  as  long  as  a 


HOUSEHOLD   CHEMISTRY  177 

precipitate  appears,  filter,  wash  slightly,  reject  the  residue,  add 
Na2HPO4  solution  to  the  clear  filtrate  to  precipitate  excess  of 
lead  as  phosphate,  and  wash.  Concentrate  the  filtrate  to  small 
bulk  (25  cc.),  cool,  transfer  to  a  separatory  funnel  and  add 
5-10  cc.  of  chloroform.  Mix  well,  and  after  settling  draw  off 
the  chloroform  layer  into  a  weighed  porcelain  dish  and  drive  off 
the  solvent  over  hot  water.  Cool  and  weigh.  Caffein  crys- 
tallizes in  minute  colorless  needles,  possessing  a  bitter  taste. 

After  removing  the  chloroform,  evaporate  some  of  the  tea 
extract  in  a  clean  porcelain  dish  over  hot  water  and  note  the 
large  amount  of  residue,  also  its  color  and  gummy  nature. 

Coffee  consists  of  the  dried,  fermented  and  roasted 
beans  of  the  Caffea  arabica — an  evergreen  shrub.  In 
the  roasting  process  flavor  is  increased  owing  to  the  con- 
version of  a  carbohydrate  constituent  to  caramel,  and  the 
development  of  caffeol,  an  oil  to  which  much  of  the  aroma 
of  coffee  is  due. 

Coffee  and  tea  contain  about  the  same  amount  of 
caffein.  In  addition  the  chief  ingredients  of  the  former 
are  caffetannic  acid,  cellulose,  fat,  gum,  protein,  and  a 
sugar. 

French  coffee  usually  contains  chicory,  the  kiln  dried 
root  of  the  wild  endive ;  the  drying  operation  produces 
caramel  at  the  expense  of  sugar  and  hence  the  water 
extract  is  dark  in  color. 

Coffee  substitutes  are  composed  of  roasted  cereals  or 
breads  with  or  without  the  addition  of  ground  roasted 
coffee.  Their  extracts  may  not  be  entirely  free  from 
caffein  and  tannin,  but  in  any  case  will  contain  less  than 
genuine  coffee.  The  bitter  taste  and  dark  color  are  due 
to  caramel. 


1/8  HOUSEHOLD   CHEMISTRY 

EXPERIMENTS  ON  COFFEE. 

Grind  the  roasted  beans  to  a  fine  powder,  throw  half  a  tea- 
spoonful  of  the  powder  into  a  vessel  holding  cool  water,  stir 
well,  and  note  whether  any  color  is  imparted  to  the  liquid 
(chicory). 

Moisten  i  tablespoonful  of  the  powder  with  cold  water,  add 
I  cup  of  warm  water,  bring  to  the  boiling-point  and  boil  2 
minutes.  Filter  through  paper  or  cotton  and  reserve  the  clear 
filtrate  for  test  as  follows : 

Decolorize  a  small  portion  with  bone-black  and  when  cold  test 
for  starch  with  iodine.  It  should  be  absent;  if  present  the 
sample  contains  cereal  or  bread. 

Test  another  portion  for  tannin  (see  tea).  Determine  pres- 
ence of  caffein  (as  under  tea),  using  finely  ground,  well  roasted 
material,  and  taking  about  double  the  amount  used  in  the  case 
of  tea.  Chill  some  of  the  clear  filtrate;  should  it  turn  cloudy, 
make  further  test  for  dextrin  with  alcohol. 

Make  warm  infusions  (not  boiled)  of  coffee,  chicory,  and  a 
blend  of  the  two.  Add  a  small  quantity  of  a  saturated  solution 
of  cupric  acetate  to  each  and  filter.  Greenish  yellow  color  indi- 
cates pure  coffee;  red  brown  indicates  chicory;  yellow  brown 
shows  a  blend  of  the  two. 

Examine  thoroughly  extracted  coffee  grounds  under  the 
microscope. 

Determine  quality  of  ash. 

Notes  on  Coffee  Making.* — Experiments  made  to  com- 
pare the  quality  and  composition  of  coffee  extract  pre- 
pared from  different  grades  of  granulation  and  by  dif- 
ferent methods  lead  to  the  following  conclusions : 

i.  The  finer  the  granulation  the  stronger  the  extract. 
The  structure  of  the  coffee  granule  appears  to  be  such 
that  fine  grinding  breaks  down  minute  compartments, 
*  Taken  from  the  Tea  and  Coffee  Trade  Journal,  Dec.  1913. 


HOUSEHOLD   CHEMISTRY  1/9 

which  yield  increased  flavor  and  color  to  the  infusion. 
For  example : 

Coffee  of  medium  granulation,  sifted  through  a  No.  6 
sieve,  gave  25  per  cent,  efficiency. 

The  same  coffee,  not  sifted,  50  per  cent,  efficiency. 

Pulverized  coffee,  100  per  cent,  efficiency. 

Therefore,  one  part  of  the  last  will  be  equal  to  four 
parts  of  the  first  or  two  of  the  second. 

2.  Fresh  granulation  is  essential.     Coffee  rapidly  de- 
preciates in  flavor. 

3.  Boiling  water  is  twice  as  efficient  in  making  the  ex- 
tract as  water  under  boiling,  e.  g.,  at  about  150°  F. 

4.  The  principal  extraction  of  value  takes  place  the 
instant  the  water  boils.     If  boiling  is  continued  the  coffee 
changes  color  and  becomes  muddy,  because  the  coarse 
fibrous  shell  is  broken  down  and  yields  undesirable  ele- 
ments to  the  infusion.     Medium  granulation  is  necessary 
in  making  a  clear  boiled  coffee. 

5.  The  use  of  egg  in  clarifying  is  not  recommended,  as 
it  does  not  improve  the  flavor.     It  is  better  to  strain  off 
the  liquor. 

The  methods  of  making  introduced  in  the  tests  were : 

Boiling. — Boiling  water  poured  on  coffee  and  the  in- 
fusion allowed  to  boil  for  a  few  minutes. 

Steeping. — Coffee  placed  in  cold  water,  brought  to  a 
boil,  and  immediately  strained  off. 

Percolating. — In  a  coffee  percolator. 

Filtration. — Boiling  water  was  made  to  drip  slowly  and 
steadily  through  pulverized  coffee  in  a  muslin  bag. 


i8o 


HOUSEHOLD   CHEMISTRY 


Scalding. — Coffee  was  added  to  actively  boiling  water, 
vigorously  stirred  for  30  seconds  and  the  infusion  filtered 
immediately. 

The  composition  of  the  infusions  was  found  to  be  as 
follows : 


Per  cent, 
extract 

Caffein 
Grains  per 
cup 

CafTetatinic 
acid 
Grains  per 
cup 

i.  Boiling  (Med.  Gran.)  •  • 
2    Boiling  (  Pulv  )  

2.63 

2   7f> 

2.58 

2-35 

7    Steeping  (Med  )  

o  «;8 

A    Steeping  (  Pulv  )  

2  t;8 

•'•o1 

5.  Percolating  (3  min.)  •  •  • 
6.  Percolating  (5  min.  )  •  •  • 
7    Piltration  (  Pulv  )  

l.85 
1.86 

*«75 

2.86 
2.91 

•35 
2.21 
2.90 

8    Scalding  (Med  )  

I  81 

9    Scalding  (Pulv  )  

i.yy 

•*-35 

t  i  r 

••9" 

From  the  above,  it  will  be  seen  that : 

1.  Boiling  yields  the  greatest  amount  of  extract,  and 
a  relatively  high  amount  of  caffein  and  caffetannic  acid. 

2.  Steeping  yields  a  lower  amount  of  caffein  than  ( i ) , 
but  about  as  much  caffetannic  acid.     With  medium  gran- 
ulation, the  least  amount  of  caffein  is  given. 

3.  Filtration  gives  less  extract  and  less  acid. 

4.  Scalding  is  intermediate  between  filtration  and  boil- 
ing. 

5.  Percolating  gives  a  low  extract  but  high  acid  and 
high  caffein.     The  reason  is  that  the  water  in  a  perco- 
lator does  not  boil  over  the  coffee,  but  passes  over  by 
force  of  condensation,  at  a  temperature  seldom  above 
150°  F.     Hence  its  power  of  extraction  is  low,  but  its 


HOUSEHOLD   CHEMISTRY 


181 


acid  and  caffein  content  will  be  relatively  high,  as  these 
bodies  are  soluble  in  cold  water.  Caffetannic  acid  is  a 
hindrance  to  digestion. 

A  second  series  of  tests  showed  the  following : 


Caffein 

Caffetannic 

Extract 

Grains  per 
cup 

Grains  per 
cup 

Boiled  (  Med  )  

Steeped  (Med  )  .  .  .  . 

O  80 

Percolated  (Fine)  (3  inin.) 

1.85 

2.86 

2.21 

Percolated  (Fine)  (5 

min.) 

1.86 

2.91 

2.90 

Filtered  (Pulv.  )  (l/2  Quan.  ) 

1.03 

1.4? 

0.19 

The  conclusion  reached  in  the  article  quoted  is  that  on 
the  whole  the  filtration  method  is  the  best  to  employ,  since 
it  uses  the  coffee  in  the  most  efficient  form  and  water 
at  its  most  efficient  temperature;  the  flavor  of  the  in- 
fusion is  superior ;  it  is  almost  tannin  free,  and  contains 
on  an  average  about  i^  grains  of  caffein  per  cup. 

Chocolate  and  Cocoa. — These  products  are  made  from 
the  fermented  and  dried  seeds  of  the  fruit  of  the  Theo- 
broma  cacao,  which  resembles  the  cucumber.  After  dry- 
ing and  husking,  the  seeds  yield  two  halves  called  "nibs." 

The  nibs  are  ground  to  a  fine  powder  under  hot  rolls, 
which  melts  the  large  quantity  of  fat  (cocoa  butter) 
present  and  produces  a  liquid  mass.  If  this  is  allowed  to 
run  into  shallow  molds  and  cooled  the  product  is  called 
chocolate  or  bitter  chocolate.  Sugar  and  vanilla  extract 
are  often  added  to  the  liquid  before  cooling,  producing 
sweet  or  edible  chocolate. 


l82  HOUSEHOLD   CHEMISTRY 

If  the  fluid  mass  of  ground  nibs  is  pressed  to  remove 
fat  and  the  remainder  is  cast  in  molds  and  afterward 
ground,  the  product  is  called  soluble  cocoa.  Alkali  in 
small  amount  is  frequently  used  in  the  effort  to  make  the 
cocoa  more  soluble,  but  this  is  a  fallacy. 

The  principal  alkaloid  in  the  cocoa  bean  is  theobromine. 
Caffein  is  present  in  small  amount. 

Cheap  grades  of  cocoa  contain  considerable  quantities 
of  starch  and  ground  cocoa  shells. 

EXPERIMENTS  ON  CHOCOLATE  AND  COCOA. 

Boil  some  of  the  finely  ground  mass  with  water,  filter  while 
hot  and  reserve  both  filtrate  and  residue  for  test. 

Tests  on  Filtrate. — For  starch,  dextrin,  sugar,  protein  matter 
and  soaps. 

Tests  on  Residue. — Dry  and  extract  fatty  matter  with  gasoline. 
Examine  extracted  residue  under  the  microscope  for  fiber. 
Determine  quality  and  amount  of  ash. 


CHAPTER  XIII. 


FERMENTS  AND  PRESERVATIVES. 

The  organisms  which  cause  the  most  common  changes 
in  our  food  materials  are  generally  known  as  yeasts, 
lactic  acid  and  vinegar  ferments.  Their  spores  are 
present  in  all  house  dust.  These  organisms  are  distin- 
guished by  the  fact  that  they  operate  in  presence  of  air, 
under  widely  varying  temperature  conditions,  and  give 
off  no  disagreeable  odors  while  their  products  are  non- 
poisonous.  It  is  true  that  putrefactive  bacteria  play 
some  part  in  the  preparation  of  our  food,  notably  in 
meats  and  cheeses,  but  great  care  must  be  observed  that 
the  process  is  kept  under  strict  control  and  allowed  to 
proceed  only  to  a  limited  extent.  The  activities  of  these 
various  organisms  are  due  to  enzymes  secreted  by  their 
cells. 

Yeast  Fermentation. — This  type  of  fermentation  is 
typically  alcoholic.  The  food  chosen  for  the  growth  of 
the  yeast  organisms  is  mostly  carbohydrate  material, 
which  is  decomposed  by  enzyme  action  to  alcohol  and 
carbon  dioxide  as  the  principal  products.  The  by-prod- 
ucts are  extremely  numerous,  and  include  succinic  acid, 
glycerol,  and  traces  of  esters,  aldehydes  and  complex 
alcohols.  The  expression  C6HUO6  — -  2C,H5OH  -f  2COa 
is  therefore  merely  general  for  yeast  action. 

In  ordinary  yeast  the  enzymes  acting  on  carbohydrate 
material  are  maltase,  invertase,  and  zymase.  There  is 
evidence  that  phosphates,  such  as  are  present  in  yeast 


184  HOUSEHOLD   CHEMISTRY 

cells,  are  necessary  to  fermentative  changes,  as  added 
phosphates  greatly  stimulate  fermentation  and  enter  into 
combination  with  monosaccharid  material  as  a  hexose- 
phosphate. 

Due  to  the  specific  action  of  the  enzymes  present, 
starch  and  lactose  are  not  acted  upon  directly  by  ordinary 
yeast;  maltose  is  changed  by  maltase  to  glucose;  cane 
sugar  is  hydrolyzed  by  invertase,  and  zymase  completes 
the  alcoholic  fermentation  of  the  monosaccharid  products. 
Different  yeasts  have  different  fermenting  action,  e.  g., 
S.  fragilis,  found  in  kefir,  has  a  lactose  enzyme. 

Yeasts  in  general  have  their  optimum  activity  be- 
tween 68°  and  90°  F. ;  the  maximum  growth  tempera- 
ture for  many  varieties  is  about  105°  F.  In  the  moist 
condition  coagulation  takes  place  at  lower  temperatures 
than  in  the  dry.  Yeasts  are  killed  more  or  less  quickly 
from  in0  to  140°  F.,  with  moist  heat.  Sterilization 
with  dry  heat  necessitates  long  continued  high  temper- 
atures, or  intermittent  sterilization.  For  pasteurization, 
it  is  well  to  maintain  for  some  time  the  lower  tempera- 
ture employed,  to  insure  uniform  heating  of  the  mass. 
Yeasts  are  not  easily  destroyed  by  cold  unless  exposed 
to  very  low  temperature  for  long  periods. 

The  rate  of  fermentation  increases  with  concentration 
of  the  sugar  up  to  a  certain  limit,  then  decreases  with 
further  concentration.  When  15  per  cent  of  alcohol  has 
been  formed  the  action  ceases,  even  though  the  mass 
contains  unchanged  carbohydrate. 

Lactic  Acid  Fermentation. — The  organisms  capable  of 


HOUSEHOLD    CHEMISTRY  185 

producing  this  form  of  fermentation  are  numerous,  and 
operate  on  various  forms  of  carbohydrate  material. 
They  have  been  found  in  milk,  beer,  distiller's  mash, 
sauerkraut,  and  other  substances.  The  forms  most 
commonly  occurring  in  milk  are  the  Streptococcus 
lacticus,  and  a  similar  organism,  Bacterium  lactis  acidi, 
which  hydrolyze  lactose,  and  convert  the  resulting  glu- 
cose almost  entirely  into  lactic  acid:  C6H12O6  ••-» 
2C3H6O3,  with  no  gas  formation.  Another  organism 
well  known  for  its  value  in  preparing  sour  milk  is  B.  bul- 
garicum.  It  hydrolyzes  lactose  and  ferments  about  92 
per  cent,  of  both  products — galactose  and  glucose — to 
lactic  acid  so  that  the  total  amount  formed  is  much 
greater  than  with  the  organisms  described  above.  These 
ferments  are  not  easily  destroyed  by  cold  but  do  not  act 
below  50°  F.  and  continue  their  work  up  to  130°  F.,  be- 
ing most  active  at  110°  F.  Conditions  for  sterilization 
and  pasteurization  are  similar  to  yeasts. 

These  organisms  represent  the  true  lactic  fermentation, 
in  which  the  by-products  are  almost  negligible.  A  modi- 
fied lactic  fermentation  is  produced  by  groups  of  in- 
testinal origin.  The  products  of  these  are  lactic  and 
other  acids,  alcohol  and  gases — lactic  acid  forming  less 
than  one  half  of  the  total. 

Salt-rising  bread*  and  sour  dough  bread  are  prepared 
by  a  method  of  spontaneous  fermentation.  The  organ- 
isms producing  fermentation  probably  vary,  but  in  some 
instances  are  those  which  develop  lactic  acid  and  gas 
*  See  Buchanan ;  Household  Bacteriology  >  and  The  Baker's 
Review,  August,  1911,  to  March,  1912. 


l86  HOUSEHOLD   CHEMISTRY 

from  sugar.  When  corn  meal  has  been  used  in  the  fer- 
menting batter,  it  is  probable  that  gas  is  produced  by  the 
Bacillus  coli. 

Acetic  Acid  Fermentation. — The  production  of  acetic 
acid  from  alcohol  is  a  type  of  bacterial  action  well 
known  in  everyday  experience.  The  souring  of  wines 
and  the  production  of  vinegar  are  illustrations  of  the 
activities  of  this  organism.  The  ferment,  commonly 
known  as  "mother  of  vinegar,"  carries  oxygen  from  the 
air  to  the  alcohol,  the  oxidation  resulting  in  acetic  acid : 

CH,CH,OH  +  O2  —  CHSCOOH  +  H2O 
It  acts  on  all  weak  alcoholic  liquids  of  10  per  cent,  and 
under.  The  temperature  conditions  are  much  the  same 
as  for  lactic  acid  (5o°-uo°  F.).  Fermentation  ceases 
when  5  per  cent,  of  acid  has  been  produced.  Conditions 
for  sterilization  and  pasteurization  are  similar  to  yeasts. 

Butyric  Acid  Fermentation. — Important  fermentative 
changes  producing  butyric  acid  are  brought  about  by  the 
action  of  many  bacteria.  Two  types  of  these  organisms 
are  recognized: 

(1)  The  non-motile  butyric  acid  bacillus,   found  in 
milk  and  in  the  soil.    It  is  an  anaerobic  form  which  fer- 
ments sugars,  starch,  and  under  some  conditions  lactic 
acid,  the  products  being  butyric  acid,  lactic  acid,  hydro- 
gen, and  carbon  dioxide.     It  liquefies  gelatin. 

(2)  The  motile  butyric  acid  bacillus,  found  in  soil, 
water,  and  cheese.    It  is  anaerobic,  does  not  liquefy  gel- 
atin, and  has  a  chemical  action  on  carbohydrates  similar 
to  the  non-motile  form. 


HOUSEHOLD    CHEMISTRY  187 

Other  forms  are  known,  of  a  pathogenic  order,  which 
act  upon  both  carbohydrates  and  proteins. 

EXPERIMENTS. 

i.  Fermentation  of  Carbohydrate  by  Yeast — Dissolve  a  con- 
siderable quantity — about  150  grams — of  commercial  glucose  or 
of  molasses  in  I  or  2  liters  of  water  in  a  good  sized  distilling 
flask.  Dissolve  one-fourth  of  a  yeast  cake,  add  to  the  solution, 
warm  to  25°  and  keep  in  a  warm  place  until  fermentation  ceases. 
Distil  over  a  water-bath,  noting  the  temperature  at  which  the 
distillate  passes  over,  and  test  the  latter  for  alcohol  by  burning 
a  portion  and  by  the  iodoform  reaction. 

Yeast — Temperature  Experiments — Prepare  four  6-inch  test 
tubes  with  perforated  corks,  bearing  tubes  bent  in  the  form  of 
an  inverted  letter  J.  Fill  three  of  the  tubes  with  a  mixture, 
prepared  from  one-half  a  yeast  cake,  one-half  tablespoonful  of 
molasses  and  a  cup  of  water.  Fill  the  fourth  with  the  same 
preparation  filtered  through  absorbent  cotton.  Allow  tubes  Nos. 
i  and  4  to  stand,  while  No.  2  is  subjected  to  a  temperature  of 
32°  F.  (produced  by  a  mixture  of  pulverized  ice  and  salt)  for 
15  minutes.  No.  3  is  boiled  for  2  or  3  minutes.  Now  place  the 
four  pieces  of  apparatus  so  that  the  delivery  tube  of  each 
reaches  to  the  bottom  of  a  test  tube  containing  about  2  inches 
of  clear  limewater,  and  allow  them  to  stand  for  at  least  12  hours 
in  a  warm  place  (90°  F.).  At  the  end  of  this  time  examine 
each  tube  of  limewater,  first  for  a  precipitate,  and  second  with 
litmus  paper.  Finally  examine  the  liquid  in  the  fermentation 
tubes,  noting  its  odor  and  general  properties. 

For  the  action  of  yeast  on  different  carbohydrates,  see  p.  98. 

Lactic  Acid. — To  about  6  ounces  of  pasteurized  milk  contained 
in  a  small  flask,  add  i  tablespoonful  of  the  liquid  obtained  by 
dissolving  one  lactobacilline  (Metchnikoff)  tablet  in  half  a  cup 
of  tepid  water.  Mix  well  and  keep  at  100°  F.  for  36  hours. 
Carefully  observe  all  changes  taking  place  and  compare  with  the 
well  known  buttermilk. 
13 


l88  HOUSEHOLD   CHEMISTRY 

Acetous  Fermentation — Make  a  weak  solution  of  alcohol  in 
water  (5  parts  of  alcohol  to  20  parts  of  water)  and  test  with 
litmus  paper ;  if  acid,  neutralize  with  a  weak  solution  of  sodium 
carbonate  and  test  a  small  portion  with  potassium  iodide  and 
potassium  hydroxide,  heat — the  odor  of  iodoform  shows  the 
presence  of  alcohol. 

Divide  the  balance  of  the  solution  into  two  equal  parts,  pour 
one  into  a  shallow  dish  and  place  the  other  in  a  well-corked 
bottle.  After  the  solutions  have  stood  for  a  week,  test  with 
litmus  paper,  and  also  by  adding  alcohol  and  warming  gently. 
Note  the  peculiar  odor  of  ethyl  acetate — odor  of  hard  cider — in 
the  first  case  but  not  in  the  latter.  Explain. 

Expose  a  small  quantity  of  beer  to  the  atmosphere  for  several 
days ;  subsequently  examine  for  acidity  with  test  paper  and  for 
acetic  acid  with  alcohol.  From  the  results  of  these  experiments 
explain  why  bottled  weak  alcoholic  beverages  keep  sweet. 

Butyric  Fermentation — Neutralize  some  sour  milk  with  chalk, 
add  a  little  decaying  cheese,  and  allow  to  stand  for  some  hours. 
The  butyric  ferment  in  the  cheese  acts  on  the  lactic  acid  in  a 
neutral  medium,  as  follows : 

2CH3CHOHCOOH  -—  C,H7COOH  +  2CO,  +  2H, 

Note  the  growing  acidity  and  odor  of  the  milk. 

All  foods  are  subject  to  the  attack  of  bacteria  and  in 
consequence  their  value  is  very  generally  seriously  im- 
paired. Methods  for  prevention  of  these  changes  have 
been  used  from  the  earliest  times  and  are  known  as 
preservation. 

At  least  two  general  types  of  process  are  in  common 
use,  vis.,  physical  and  chemical.  To  the  first  class  be- 
long such  methods  as  drying,  cooling,  and  canning.  These 
processes  are  applicable  to  all  kinds  of  foods,  possess 
high  efficiency  and  make  very  slight  changes  in  flavor, 
appearance  and  composition.  Unfortunately,  food  ma- 


HOUSEHOLD   CHEMISTRY  189 

terials  preserved  in  any  of  these  ways  will  change  very 
rapidly  with  a  slight  variation  of  physical  conditions, 
hence  the  effects  are  not  permanent.  The  second  class 
involves  such  change  of  chemical  conditions  that  no  mat- 
ter what  physical  changes  may  occur,  decomposition  can- 
not take  place.  The  results  are  permanent  but  are  ac- 
complished at  the  expense  of  flavor,  appearance,  etc. 

So  general  has  the  use  of  chemical  preservatives  be- 
come that  a  brief  discussion  of  the  subject  seems  nec- 
essary. The  best  known  and,  as  generally  conceded, 
harmless  are:  alcohol,  vinegar,  sugar,  and  salt  (NaCl). 
With  the  exception  of  vinegar  (acids  generally  being 
inimical  to  bacteria)  the  action  seems  to  depend  on  mak- 
ing the  protein  matter  present  insoluble;  hence  we  find 
the  quantity  of  the  preservatives  important.  Well  known 
operations  are  as  follows : 

Alcohol — 50  per  cent.  "Brandying." 

Salt — dry  or  supersaturated  solution  "Pickle." 

Sugar — syrup — solutions  of  25  per  cent,  or  more. 

Less  well  known  methods  accomplish  similar  results 
by  using  very  small,  in  some  cases  minute  proportions, 
of  other  chemical  agents ;  but  the  actual  chemical  opera- 
tion can  only  be  surmised  in  most  cases.  Included  in  this 
list  are :  borates,  fluorides,  sulphites,  peroxides,  formalde- 
hyde, benzoates,  salicylates  and  creosote.  It  may  be  as 
well  to  observe  that  the  use  of  spices,  for  instance  in 
mince  meat,  is  certainly  parallel  with  benzoates  and 
salicylates. 

Boric  acid,  borax  and  borates  are  efficient  in  small 


I9O  HOUSEHOLD    CHEMISTRY 

quantities — as  low  as  I  per  cent.     Their  use  in  preserving 
meats  is  not  permitted  at  present  in  the  United  States. 

Sulphites  can  not  now  be  used  for  giving  cut  meat  a 
red  appearance. 

It  has  not  been  proved  that  sodium  benzoate  is  danger- 
ous in  the  amounts  used  for  food  preservation,  and  it  is 
allowed  under  the  Food  and  Drugs  Act,  provided  the 
label  states  the  fact.  Salicylic  acid  is  not  allowed. 

Wood  tar  creosote  is  very  efficient  as  a  non-poisonous 
preserver  of  meat. 

EXPERIMENTS. 

Alcohol  and  vinegar  are  first  separated  by  distillation  and  then 
identified  by  well  known  methods.  Sugar  and  salt  may  also  be 
determined  by  diluting,  filtering  and  testing  the  clear  filtrate. 

Borates. — Ash  some  of  the  substance,  cool,  make  strong  water 
extract,  filter  if  necessary  and  neutralize  with  dilute  HC1.  Dip 
a  strip  of  turmeric  paper  in  this  liquid,  remove  and  dry  by  steam 
heat.  (This  may  be  accomplished  by  wrapping  the  moist  paper 
around  the  upper  part  of  a  test  tube  partly  filled  with  water 
and  boiling  gently.)  The  paper  turns  pink  on  the  edges. 

Or  moisten  the  ash  in  the  dish  with  alcohol,  add  8  to  10  drops 
of  glycerine,  mix  well  with  a  glass  rod  and  ignite  the  mass  with 
a  match  or  Bunsen  burner.  Note  the  yellow  flame  with  a  green 
edge,  characteristic  of  borates. 

Fluorides. — Mix  the  liquid  or  solid  mass  with  an  excess  of 
limewater,  evaporate  to  dryness,  ignite,  cool  and  make  the  etch- 
ing test. 

Sulphites. — If  present  in  quantity,  they  are  distinguished  by 
their  odor  and  taste,  "sulphur  match,"  especially  on  warming. 

For  small  amounts  of  sulphites,  mix  with  bromine  water,  boil 
off  excess  and  test  for  sulphates.  Sulphates  may  be  present  in 
the  original  liquid,  in  which  case  precipitate  by  BaCl2  and  HC1, 
filter  and  use  the  clear  filtrate  as  above. 

Formaldehyde. — See  page  199. 


HOUSEHOLD   CHEMISTRY  IQI 

Bensoates. — Carefully  mix  liquid  substance  with  one-tenth  of 
its  volume  of  chloroform  and  a  few  drops  of  oil  of  vitriol. 
Avoid  violent  shaking  (mix  with  a  rotary  motion).  Allow  the 
mixture  to  remain  quiet  until  chloroform  layer  separates. 
Remove  some  of  this  layer  with  a  pipette  and  evaporate  it  in  a 
clean  porcelain  dish  over  hot  H2O.  Note  the  flat  crystalline 
plates  of  benzoic  acid,  which  give  off  a  pungent  odor  on  heating. 
Examine  the  original  mixture  in  the  flask,  note  any  violet  color 
between  layers  of  acid  liquid  and  chloroform.  This  indicates 
salicylic  acid. 

Both  benzoic  and  salicylic  acids  are  not  present  in  the  same 
liquid. 

TESTS  FOR  PURITY  OF  CERTAIN  FOODS. 

Sanitary  Condition  of  Milk — The  presence  of  a  large  number 
of  bacteria  in  milk  indicates  stateness  or  an  insanitary  condition. 
The  following  test  will  give  some  indication  of  its  purity :  First 
sterilize  all  utensils  used  by  keeping  in  boiling  water  l/t  hour. 
Warm  I  pint  of  milk  to  body  temperature  and  add  one  junket 
tablet  which  has  been  dissolved  in  I  tablespoon  of  cooled  boiled 
water.  Stir  until  thoroughly  mixed  and  allow  to  stand  quietly 
until  the  milk  has  clotted.  Cut  the  curd  in  cross-sections  with 
a  knife  and  carefully  pour  off  the  whey.  From  time  to  time, 
draw  off  the  whey  as  it  accumulates.  When  the  curd  is  com- 
pact, cut  it  with  a  knife  and  observe  its  condition.  If  it  is  firm 
and  smooth  with  but  few  holes,  the  milk  does  not  contain  an 
abnormal  number  of  bacteria.  If  the  curd  has  a  spongy  appear- 
ance, bacteria  are  present  which  have  produced  gas.  Place  a 
tablespoon  of  the  curd  in  water;  if  it  sinks,  the  milk  is  compara- 
tively clean;  if  it  floats,  the  milk  is  stale  or  in  an  insanitary 
condition. 

Formalin  in  Milk — See  page  166. 

Genuine  Butter. — See  page  140. 

Coal  Tar  Coloring  in  Butter,  etc — i.  The  custom  of  coloring 
butter  is  very  largely  practiced  in  the  United  States.  Vegetable 
dyes,  such  as  annatto,  have  been  employed  in  the  past,  but  coal 


192  HOUSEHOLD   CHEMISTRY 

tar  products  (anilin  dyes)  are  now  quite  frequently  used.  Coal 
tar  yellow  may  be  detected  by  the  following  experiment :  Into 
a  weak  solution  of  alcohol,  put  i  teaspoon  of  butter,  a  small 
amount  of  cream  of  tartar,  and  bits  of  white  silk  or  wool.  Boil 
the  mixture.  If  coal  tar  coloring  is  present,  the  samples  will 
be  dyed. 

2.  Melt  a  teaspoonful  of  butter  in  a  test  tube  at  low  heat.  Add 
an  equal  volume  of  Low's  reagent  (mix  4  parts  CHaCOOH, 
I  part  H.SCX)  ;  shake  well,  heat  nearly  to  boiling,  and  set  aside 
to  separate  into  layers.  The  acid  layer  will  be  colored  red  if 
azo  dyes  have  been  used.  Pure  butter  gives  a  faint  blue  tinge. 

Annatto — Place  about  100  cc.  of  milk  in  a  cylinder,  make 
alkaline  with  sodium  carbonate  solution,  insert  a  long  strip  of 
heavy  white  filter  paper  and  allow  to  stand  in  a  dark  place  for 
about  12  hours.  Withdraw  the  paper,  wash  gently  in  running 
water  and  observe  against  a  fresh  piece  of  the  same  kind  of 
paper.  If  annatto  is  present,  the  paper  will  have  taken  up  some 
of  the  color.  Prove  by  dipping  the  strip  into  a  solution  of 
stannous  chloride.  It  becomes  pink. 

Alum  in  Food  Products — Make  water  solution  and  follow 
method  under  Baking  Powders,  page  174. 

Copper  Compounds  in  Canned  Goods — As  a  rule,  coloring  matter 
is  not  added  to  domestic  goods.  Imported  varieties,  as  green 
peas,  having  an  intense  color,  usually  have  copper  added  in 
small  amounts.  It  may  be  detected  by  adding  a  few  drops  of 
hydrochloric  acid  to  a  portion  of  the  material  and  dropping  in 
a  bright  steel  nail  or  the  blade  of  a  knife.  If  copper  salts  are 
present,  a  reddish  color  will  appear  on  the  steel. 

Purity  of  Olive  Oil — See  Halphen's  Test,  page  139. 

Purity  of  Extracts — Vanilla.— (a}  Vanilla  extract  shows  a 
nearly  colorless  foam  on  shaking;  in  case  vanillin  has  been  used 
the  foam  will  be  colored  due  to  the  addition  of  caramel  for  the 
purpose  of  imitating  the  vanilla  color. 

(&)  Leach's  Test.— To  40  cc.  of  the  sample  add  an  equal 
volume  of  normal  lead  acetate  (dissolve  189.5  grams  of 
Pb(C2H3O2)2,  3H2O  in  water  and  make  up  to  i  liter).  If  a 


HOUSEHOLD   CHEMISTRY  IQ3 

precipitate   settles   out   the   vanilla   is   pure;    vanillin   gives   no 
precipitate. 

Lemon  Extract — Test  by  adding  a  few  drops  of  the  extract 
to  water.  The  true  lemon  oil  is  insoluble  in  water,  and  a  milky 
appearance  results.  Artificial  lemon  extract  gives  a  clear  water 
solution. 

Saccharin — This  substance  may  be  added  to  canned  products 
in  place  of  sugar.  It  is  a  coal  tar  product  having  several  hun- 
dred times  the  sweetening  power  of  cane  sugar.  To  determine 
its  presence  shake  15  or  20  cc.  of  the  suspected  liquid  in  a  flask 
with  an  equal  volume  of  chloroform.  Saccharin  is  soluble  in 
chloroform ;  while  sugar  is  insoluble.  With  a  medicine  dropper 
remove  some  of  the  chloroform  which  has  settled  to  the  bottom. 
By  gently  heating  in  a  porcelain  dish,  evaporate  the  chloroform. 
Taste  the  residue;  if  sweet,  saccharin  is  present. 

Freshness  of  Eggs — Candling  is  one  of  the  methods  most 
frequently  used.  In  a  darkened  room  hold  an  egg  between  the 
eye  and  an  artificial  light.  A  fresh  egg  should  appear  unclouded, 
homogeneous,  and  almost  translucent.  If  dark  spots  are  found, 
it  is  stale.  A  rotten  egg  appears  dark  colored. 

Against  the  larger  end  of  a  fresh  egg  between  the  shell  and 
the  lining  membrane,  a  small  air  cell  should  be  distinctly  visible. 
In  an  egg  which  is  not  perfectly  fresh,  this  space  is  filled  with 
the  egg  substance,  unless  the  egg  has  been  stored  with  the  large 
end  up. 

Salt  solution  test :  As  the  density  of  an  egg  decreases  by  the 
evaporation  of  moisture,  its  freshness  may  be  approximately  esti- 
mated by  placing  it  in  brine.  Prepare  the  salt  solution  by  dis- 
solving 2  ounces  of  salt  to  I  pint  of  water.  Immerse  the  egg 
in  the  solution.  A  perfectly  fresh  egg  will  sink;  if  several  days 
old,  it  will  swim  just  immersed  in  the  liquid;  if  stale,  it  will 
float  on  the  surface. 

Shake  an  egg,  holding  it  near  the  ear.  The  contents  of  a  fresh 
egg  should  not  move.  If  a  slight  movement  can  be  detected,  it 
is  somewhat  stale;  if  it  rattles,  the  egg  is  spoiled. 


194  HOUSEHOLD   CHEMISTRY 

Open  the  egg  and  observe  the  odor  and  taste.  If  there  is  a 
tendency  for  the  white  and  yolk  to  run  together,  the  egg  is  not 
fresh,  or  the  hen  has  been  improperly  fed. 

Coffee — See  Experiments,  page  178. 

Gelatin  in  Ice  Cream Page  167. 

Vinegar  has  been  very  largely  subject  to  substitution  and  imi- 
tation. The  best  varieties  on  our  market  are  cider,  wine,  and 
malt  vinegar.  Substitution  may  be  detected  by  slowly  evapo- 
rating almost  to  dryness  ^  cup  of  vinegar  in  a  small  evaporating 
dish  and  examining  the  warm  residue.  If  there  is  a  distinct 
odor  of  baked  apples,  it  is  cider  vinegar ;  of  grapes,  it  is  wine ; 
and  of  malt,  the  product  is  malt  vinegar.  Distilled  vinegar  gives 
a  burnt  sugar  odor ;  no  residue  indicates  synthetic  vinegar. 


CHAPTER  XIV. 


DISINFECTANTS  AND  DISINFECTION. 

These  terms  apply  to  the  destruction  of  bacterial  or- 
ganisms and  their  spores.  Some  confusion  of  ideas 
exists  with  regard  to  the  respective  action  of  disinfec- 
tants and  antiseptics.  A  disinfectant  is  a  germicide;  an 
antiseptic  retards  or  prevents  bacterial  activity.  A  de- 
odorant simply  absorbs  or  covers  up  noxious  vapors. 

Physical  Methods  of  Disinfection  or  Antisepsis. — Sun- 
light.— The  direct  rays  of  the  sun  are  powerful  enemies 
of  bacteria,  the  bacillus  of  tuberculosis,  for  example, 
being  killed  by  sunlight. 

Dry  Air. — Dry  air  arrests  the  activities  of  bacteria  by 
removing  conditions  of  moisture  favorable  for  their 
growth,  and  oxidizes  the  products  of  their  action  through 
the  work  of  aerobic  organisms  in  the  air. 

Cold  Storage. — This  is  an  efficient  temporary  method 
of  inhibiting  bacterial  activity.  It  should  be  understood 
that  freezing  and  cold  storage  are  not  the  same.  In 
freezing,  the  expansion  of  the  ice  crystals  disrupts  the 
structure  of  food  and  leaves  it  open  to  attack.  Food 
that  has  been  frozen  should  therefore  be  consumed  as 
soon  as  possible  after  thawing. 

Pasteurisation. — Bacteria  likely  to  be  present  in  impure 
milk  are  killed  by  a  temperature  of  60°  to  70°  main- 
tained for  20  minutes  to  I  hour,  according  to  the  tem- 
perature employed.  The  organisms  which  escape  are 
comparatively  harmless  in  effect. 


196  HOUSEHOLD   CHEMISTRY 

Boiling. — Typhoid  and  tuberculosis  bacteria  are  killed 
by  boiling  for  I  minute.  Drinking  water  and  milk  are 
likely  to  be  sterilized  by  this  treatment.  To  destroy  the 
spores  of  some  other  forms  of  pathogenic  bacteria,  boil- 
ing must  be  repeated  on  two  or  three  successive  days. 

Some  Common  Antiseptics. — Salt,  sugar,  spices,  vinegar, 
and  creosote  have  considerable  efficiency  as  antiseptics. 
The  power  of  salt,  sugar,  and  vinegar  to  inhibit  the  action 
of  bacteria  depends  upon  the  strength  of  their  solutions. 

Chemical  Means  of  Disinfection. — Mercuric  Chloride, 
or  corrosive  sublimate,  is  one  of  the  most  powerful  of 
germicides.  Its  use  is  limited,  partly  because  it  is  a 
violent  poison,  partly  by  its  tendency  to  form  a  precipitate 
with  many  inorganic  and  organic  substances,  such  as 
hard  water,  alkalies,  protein  bodies,  etc.  A  solution  of 
one  part  of  mercuric  chloride  in  one  thousand  parts  of 
water  is  commonly  employed. 

Carbolic  Acid. — This  is  frequently  used  in  very  dilute 
solution  as  an  antiseptic  wash,  as  a  powerful  antiseptic  in 
a  strength  of  i  to  400,  or  as  a  germicide  in  stronger 
solution,  such  as  5  per  cent. 

Formaldehyde. — Formaldehyde  is  antiseptic  in  weak 
solution,  and  germicidal  in  the  40  per  cent,  solution  called 
formalin.  For  room  disinfection  the  formaldehyde  gas 
is  used,  produced  by  lamps  which  pass  methyl  alcohol 
vapor  and  air  over  hot  oxidized  copper,  or  by  heating 
paraform.  This  substance  is  a  solid  polymer  of  form- 
aldehyde, which  gives  off  the  gas  when  heated.  Form- 
aldehyde is  also  produced  from  formalin  heated  under 


HOUSEHOLD   CHEMISTRY  IQ7 

pressure,  or  treated  with  dehydrating  agents  to  cause 
an  evolution  of  the  gas. 

Sulphur  Dioxide. — This  is  a  powerful  disinfectant,  but 
has  the  disadvantage  of  being  also  a  strong  bleaching 
agent,  and  therefore  cannot  be  used  in  the  presence  of 
colors.  The  gas  is  produced  by  burning  sulphur,  com- 
monly in  the  form  of  a  sulphur  candle.  It  is  irrespirable, 
and  has  produced  fatal  results  when  in  the  proportion  of 
about  5  per  cent,  in  air.  To  do  away  with  the  necessity 
of  using  fire  to  produce  sulphur  dioxide,  its  solution  in 
water  as  sulphurous  acid  is  frequently  used.  This  acid 
is  unstable,  and  when  exposed  to  the  air  gives  off  sulphur 
dioxide  and  water. 

Copper  Sulphate. — This  compound  ranks  next  to  mer- 
curic chloride  in  antiseptic  power.  It  is  soluble  in  four 
parts  of  water,  and  in  i  per  cent,  solution  is  disinfectant ; 
in  weak  solution,  e.  g.,  o.i  per  cent.,  it  is  antiseptic  in  most 
cases. 

Zinc  Chloride  is  strongly  antiseptic  and  disinfectant, 
and  is  useful  for  drains.  A  solution  of  i  to  5  per  cent, 
is  employed  for  ordinary  antiseptic  purposes.  Zinc  oxide 
is  much  used  in  the  preparation  of  cold  creams  and  oint- 
ments, and  is  a  mild  antiseptic. 

Hydrogen  Peroxide  is  a  powerful  oxidizing  agent,  as  it 
decomposes  into  water  and  nascent  oxygen.  It  has  a 
bleaching  action  on  fabrics,  but  is  not  as  destructive  to 
the  material  as  are  Javelle  water  or  bleaching  powder. 
As  a  disinfectant  it  is  comparatively  slow  in  its  action, 
but  the  evolution  of  oxygen  is  hastened  by  the  addition 
of  a  small  amount  of  an  alkali,  such  as  borax,  to  the 


198  HOUSEHOLD   CHEMISTRY 

solution.  In  dilute  solution  hydrogen  peroxide  is  non- 
poisonous. 

"Chloride  of  Lime"  or  Bleaching  Powder. — So-called 
chloride  of  lime,  used  for  disinfecting  purposes,  is  cal- 
cium hypochlorite,  Ca(ClO)2.  A  similar  compound, 
sodium  hypochlorite,  is  known  as  Javelle  water.  The 
action  of  both  depends  upon  the  available  chlorine  they 
contain,  which  when  set  free  unites  with  water  to  form 
eventually  hydrochloric  acid  and  nascent  oxygen.  The 
carbon  dioxide  of  the  air,  or  other  acid  present,  is  neces- 
sary to  bring  around  the  reaction.  Using  acid : 

Ca(ClO),  -f  2HC1  •—  CaCl,  -f  zHCIO 
2HC1  +  aHCIO  -—  2HaO  +  2C12 

Cl,  -f  H,O  -~  2HC1  -f  O. 

Both  hypochlorites  are  strong  bleaching  agents  and  are 
especially  destructive  to  wool  and  silk  fabrics.  Cotton 
and  linen  materials  are  not  seriously  affected,  but  should 
be  rinsed  free  from  bleaching  powder  or  Javelle  water  if 
these  are  used  for  disinfecting  clothes.  The  latter  solu- 
tion is  better  for  this  purpose.  Bleaching  powder  is 
often  used  for  drains  in  about  10  per  cent,  solution. 

Washing  Soda. — In  the  strength  used  in  the  laundry, 
washing  soda  has  little  antiseptic  effect,  but  is  efficient 
in  about  2  per  cent,  hot  solution  as  a  disinfectant  for 
washing  floors  and  walks,  milk  cans,  etc. 

Soap  has  considerable  antiseptic  power.  So-called  dis- 
infectant soaps  have  little  advantage  over  ordinary  pure 
soaps  unless  the  proportion  of  disinfecting  ingredient 
is  high,  and  it  is  in  readily  soluble  form. 


HOUSEHOLD   CHEMISTRY  I9Q 

Tests  for  Disinfectants. 

On  account  of  the  small  quantities  of  material  usually 
employed,  many  of  the  ordinary  analytical  tests  fail  to 
give  conclusive  results.  Hence  the  following  methods 
are  suggested,  as  being  more  reliable  in  the  majority  of 
cases. 

Mercuric  Chloride.  (Found  usually  in  one  or  two  parts,  or 
less,  per  thousand.) — To  50  cc.  of  the  solution  in  a  large  test 
tube  add  a  few  cc.  of  a  mixture  of  equal  parts  of  weak  potas- 
sium iodide  and  ammonium  chloride  solutions  (each  i  per  cent.) 
and  immediately  2  or  3  drops  of  caustic  soda.  A  yellow  color  or 
brown  precipitate  developing  after  a  few  minutes'  standing  indi- 
cates mercury.  It  will  be  noticed  that  this  test  is  a  reversal  of 
Nessler's  test. 

Carbolic  Acid. — To  the  clear  liquid  add  bromine  water  in  slight 
excess  and  immerse  in  hot  water  until  all  odor  of  bromine  is 
dissipated.  A  white  bulky  precipitate  of  bromphenol  indicates 
carbolic  acid. 

Formaldehyde  is  best  indicated  by  the  violet  band  appearing 
as  a  zone  when  the  liquid  containing  the  aldehyde  is  carefully 
poured  upon  a  large  volume  (10  cc.)  of  commercial  concentrated 
sulphuric  acid  (oil  of  vitriol)  held  in  a  test  tube.  The  color  is 
due  to  ferric  salt  always  present  in  the  crude  form  of  the  acid. 

Sulphur  Dioxide  or  Sulphites — Indicated  by  warming  the  acidi- 
fied (HC1)  solution — an  odor  of  burning  sulphur  is  apparent. 
Or  by  adding  barium  chloride  to  the  acidified  solution,  boiling, 
and  filtering  off  the  first  precipitate  (a  precaution  necessary  due 
to  the  presence  of  sulphates),  finally  adding  a  few  drops  of 
nitric  acid  to  the  clear  filtrate  and  boiling  again  until  oxides  of 
nitrogen  and  chlorine  are  expelled.  A  white  precipitate  of 
barium  sulphate  remains,  insoluble  in  hydrochloric  acid. 

Copper  Sulphate — Indicated  by  a  deep  blue  color  on  adding 
ammonium  hydroxide  in  excess,  or  by  a  reddish  brown  precipitate 
in  potassium  ferrocyanide  solution  acidified  with  acetic  acid. 


200  HOUSEHOLD   CHEMISTRY 

Ferrous  Sulphate — Indicated  by  a  deep  blue  precipitate  in 
contact  with  dilute  potassium  ferricyanide  solution,  which  decom- 
poses on  addition  of  sodium  hydroxide  and  leaves  a  brownish 
residue. 

Permanganates.  (Alkaline  potassium  or  sodium). — Impart  a 
pinkish  color  to  the  liquid  even  in  dilute  solution.  The  color 
is  quickly  discharged  on  adding  a  mixture  of  dilute  sulphuric 
and  oxalic  acids  and  warming,  or  by  a  few  drops  of  fresh 
ferrous  sulphate  solution  acidified  with  dilute  sulphuric  acid. 

Hydrogen  Peroxide — Indicated  by  the  deep  blue  shade  imiparted 
to  ether  when  in  contact  with  an  acidified  mixture  of  potassium 
dichromate  and  peroxide. 

Bleaching  Powder  ("Chloride  of  Lime") — Sets  free  the  halogen 
from  potassium  or  sodium  iodides.  If  chloroform  is  added  the 
iodine  dissolves  in  it  with  a  violet  color.  In  the  presence  of 
starch,  the  iodide  of  starch  (blue  color)  is  formed. 


CHAPTER  XV. 


CLEANSING  AGENTS. 

The  number  of  compounds  put  on  the  market  for 
household  use  in  cleansing  and  allied  operations  is  con- 
stantly increasing,  and  in  many  cases  extravagant  claims 
are  made  with  regard  to  the  efficacy  of  the  preparations. 
The  public  is  led  to  believe  that  each  one  represents  the 
discovery  of  a  new  and  powerful  detergent.  As  a  matter 
of  fact,  analyses  of  these  preparations  show  that  they 
are  merely  variations  in  combination  of  a  few  well  known 
cleansing  agents.  A  general  classification  of  cleansers 
and  similar  compounds  reduces  them  to  a  few  principal 
groups : 

1.  Soaps  and  soap  powders. 

2.  Scouring  powders. 

3.  Metal  polishes. 

4.  Bleaches  and  stain  removers. 

5.  Grease  solvents. 

6.  Bluings. 

Soap  and  Soap  Powders. — As  shown  in  Chapter  IX, 
soaps  are  a  product  of  the  saponification  of  a  fat  by  an 
alkali.  Sodium  or  potassium  hydroxide  is  commonly 
used.  The  type  formation  of  the  soap  is  as  follows : 

(HOH) 

(1)  Fat  »-»  fatty  acid  -f-  glycerol. 

(2)  Fatty  acid  +  alkali  »-»•  soap. 

It  will  be  seen  that  glycerol  is  a  by-product.  It  is 
recovered  in  the  commercial  method  of  soapmaking,  a 


2O2  HOUSEHOLD   CHEMISTRY 

process  which  gives  the  market  its  chief  supply  of  this 
commodity. 

The  Cleansing  Action  of  soap  is  both  physical  and 
chemical.  Its  solution  in  water  acts  as  an  emulsifying 
agent,  loosening  and  removing  dirt  particles.  Chemically, 
soaps  are  salts  of  a  strong  base  and  a  weak  acid,  and  as 
such  dissociate  in  water  with  some  hydrolysis,  e.  g. : 

C17HMCOONa  +  HOH  -~  C17HMCOOH  +  NaOH. 

The  alkali  set  free  may  form  additional  soaps  with  free 
fatty  acids  present  in  the  greasy  impurities  of  the  article 
to  be  cleansed. 

Soap  powders  contain  dry  pulverized  soap,  together 
with  an  excess  of  sodium  carbonate  in  the  hydrated  form. 
They  may  or  may  not  contain  insoluble  mineral  matter — 
clay,  sand,  etc. — and  trifling  amounts  of  borax. 

Manufacture  of  Soap. — Two  classes  of  water-soluble 
soaps  are  recognized — hard,  or  soda,  and  soft,  or  potash 
soaps.  In  the  former  the  harder  fats  and  non-drying 
oils  are  used  as  a  rule;  for  the  latter  vegetable  drying 
oils  and  marine  animal  oils  are  utilizable.  In  the  manu- 
facture of  hard  soaps  two  methods — the  cold  process  or 
boiling — may  be  employed.  The  hot  process  is  the  usual 
commercial  method,  as  the  soap  produced  is  more  apt 
to  be  uniform  in  appearance  and  quality,  and  glycerol 
can  be  recovered  as  a  by-product.  The  cold  process 
gives  a  simple  and  quick  method  for  household  use,  and 
if  operated  with  intelligence  gives  a  good  neutral  soap, 
which  contains  the  glycerol. 


HOUSEHOLD    CHEMISTRY  2O3 

Boiled  Soap. — The  saponification  process  is  divided 
into  at  least  four  stages,  although  a  number  of  intermed- 
iate stages  called  "washes"  are  frequently  introduced  to 
remove  impurities. 

The  four  changes  are  known  as : 
Stock  change. 
Rosin  change — where  no  rosin  is  used  this  change 

is  replaced  with  a  wash. 
Strength  change. 
Finish. 

Stock  Change. — The  required  amount  of  mixed  tallow 
and  grease  or  oil  are  melted  together  in  large  iron  kettles 
or  tanks  by  the  aid  of  steam  coils,  the  lye  is  added  and 
the  whole  mass  boiled  until  it  is  saponified ;  at  this  stage 
the  mass  of  boiling  soap  has  a  peculiar  smooth  appear- 
ance called  "closed."  Pickle  is  now  added,  until  the 
contents  of  the  kettle  separate  into  small  broken  grains ; 
this  stage  is  called  "open  or  grained."  Heat  is  turned 
off  and  the  kettle  allowed  to  cool ;  when  cold  there  will 
be  two  layers,  the  upper  one  of  soap,  floating  on  the 
salt  lye — this  latter  is  called  "spent  lye"  and  should  be 
almost  neutral.  From  it  glycerine  and  salt  may  be  ex- 
tracted. The  spent  lye  is  then  drawn  off  from  the  bottom 
of  the  kettle,  leaving  the  soap  for  the  next  operation.  If 
no  rosin  is  to  be  used  the  "wash  change"  takes  place  at 
this  point;  this  consists  in  adding  water,  boiling  to  a 
"close"  and  then  salting  out  and  settling  as  before;  the 
wash  lye  is  worked  up  for  salt  and  glycerine. 

Rosin  Change. — Soap  from  previous  operation  receives 
14 


2O4  HOUSEHOLD   CHEMISTRY 

an  addition  of  fresh,  strong  lye,  is  heated  to  boiling  and 
the  rosin  in  lumps  thrown  into  the  kettle;  only  just  enough 
lye  to  saponify  the  rosin  is  used;  the  amount  of  rosin 
varies  but  usually  equals  the  weight  of  the  tallow  and 
grease.  Boiling  is  continued  until  rosin  is  saponified,  and 
then  pickle  is  added  to  grain ;  the  kettle  stands  to  cool ;  the 
rosin  fat  soap  rises  as  before  and  the  rosin  lye  is  drawn 
off  and  worked  for  salt  and  traces  of  glycerine. 

Strength  Change. — The  rosin  fat  soap  is  now  boiled 
with  fresh  strong  lye  until  saponification  is  complete. 
It  is  always  found  that  small  amounts  of  fat  and  rosin 
escape  saponification  in  the  earlier  stages  unless  these  are 
unduly  prolonged.  Kettle  is  cooled  and  the  soap  which 
has  been  grained  or  open  condition  throughout  this  oper- 
ation (due  to  strong  lye)  rises;  when  cold  the  strong  lye 
is  drawn  off  and  used  to  start  the  saponification  in  the 
stock  change.  This  lye  is  often  mixed  with  that  coming 
from  the  strength  change. 

Finish. — The  thoroughly  saponified  grained  soap  still 
contains  strong  lye  and  many  impurities;  and  this  is 
removed  by  melting  and  adding  water  carefully  until  the 
soap  "closes,"  or  loses  its  grained  structure.  The  kettle 
is  allowed  to  cool  very  slowly,  being  kept  perfectly 
quiet  for  at  least  48  hours.  During  this  time  three 
layers  are  formed,  the  upper  consisting  of  pure  soap,  the 
intermediate  of  impure  dark  soap  called  "nigre,"  which 
may  be  sold  as  such  or  bleached  in  a  subsequent  opera- 
tion, and  a  very  small  amount  of  strong  alkaline  lye 
called  the  nigre  lye,  which  is  generally  thrown  away. 


HOUSEHOLD   CHEMISTRY  205 

The  finished  soap  is  either  run  into  iron  box  moulds, 
stirred  well,  and  allowed  to  cool  and  set  thoroughly,  and 
then  cut ;  or  is  run  into  a  "crutcher"  or  mixing  machine, 
where  various  additions,  such  as  sal  soda,  silicate,  sa- 
ponified rosin,  etc.,  are  made.  From  this  machine  the 
mixture  is  run  into  frames,  cooled  and  cut. 

Half  Boiled  Soap. — Much  of  the  ordinary  toilet  soap  is 
made  by  this  process,  which  is  as  follows : 

The  requisite  quantity  of  fat,  tallow,  grease,  cotton 
seed  or  coconut  oil  is  heated  gently  in  a  jacketed  steam 
kettle,  enough  very  strong  lye  usually  mixed;  potash  or 
soda  is  gradually  added  and  stirred  vigorously ;  the  oper- 
ation is  complete  when  the  hot  soap  is  clear  and  will  run 
in  long  strings  from,  the  trowel  or  stirrer.  The  mixture 
is  now  ladled  into  frames  and  allowed  to  cool  and  set. 
When  cold  it  is  removed  from  the  frame,  cut  into  strips, 
dried,  chipped,  milled  between  stone  rollers.  In  the  mill- 
ing operation,  coloring  matter  and  perfumery  are  added, 
although  for  cheap  soaps  these  additions  may  be  made  in 
the  kettle  after  saponification.  After  milling  the  soap 
goes  through  the  "plotter,"  which  forms  it  into  long  bars 
and  cuts  these  into  convenient  lengths  for  pressing.  It 
will  be  noted  that  the  glycerine  remains  with  the  finished 
soap  in  this  process.  The  best  toilet  soap  is  made  by  the 
full-boiled  process. 

Average  Analyses. — The  average  compositions  of  a 
white  laundry  soap  of  good  quality  and  a  yellow  soap 
containing  rosin  are  given  below  for  comparison: 


2O6 


HOUSEHOLD   CHEMISTRY 


Rosin  soap 
per  cent. 

White  soap 
per  cent. 

Water  

30.0 
30.0 
35-o 
3-5 

I.O 

o.5 

15—25 
85-75 

Na  CO    . 

Mineral  matter  including  NaCl  

IOO.O 

IOO.O 

Use  of  Rosin. — Rosin  is  cheaper  than  soap  grease,  and 
is  introduced  primarily  as  a  filler.  It  is  properly  classed 
as  an  adulterant.  By  its  presence  more  water  can  be 
incorporated  with  the  soap,  hence  rosin  soaps  soften  and 
waste  away  rapidly.  It  is  not  strictly  a  detergent,  ex- 
cept as  it  aids  in  making  a  suds,  and  its  continued  use 
has  a  yellowing  effect  on  white  fabrics.  Based  on  the 
amount  of  actual  soap  contained  in  soaps  of  this  class, 
they  cost  more  per  pound  than  a  good  grade  of  white 
soap. 

Cold  Soaps. — For  the  production  of  a  neutral  soap  by 
this  process,  the  correct  combining  amounts  of  fat  and 
alkali  must  be  determined.  The  mean  saponification  num- 
bers of  the  fats  and  oils  commonly  used  call  for  a  pro- 
portion of  i  gram  of  fat  to  0.195  gram  of  KOH,  or 
0.139  gram  of  NaOH,  i.  e.,  ratios  of  5:  I  and  7:1  re- 
spectively. Therefore,  in  practice,  5  units  of  fat  by 
weight  combine  with  i  unit  of  caustic  potash,  or  7  units 
with  one  of  caustic  soda.  This  calculation  is  approxi- 


HOUSEHOLD   CHEMISTRY  2O/ 

mated  by  taking  the  combining  weights  of  the  interacting 
substances : 

C^H,,.  COOH  +  NaOH  —  C17HS5COONa  +  H,O. 

284  40 

Here  284  units  of  weight  combine  with  40,  giving  a 
ratio  of  7:  i. 

In  round  numbers,  for  7  pounds  of  fat,  use  I 
pound  of  caustic  soda,  dissolved  in  water  to  a  suitable 
bulk.  Crude  caustic  soda,  costing  a  few  cents  per  pound, 
can  usually  be  obtained.  The  consistency  of  the  fat 
largely  determines  the  amount  of  water  which  may  be 
incorporated;  a  fat  liquid  at  ordinary  temperatures  will 
take  up  only  about  enough  to  dissolve  the  alkali,  more 
solid  fats  will  hold  water  in  amounts  varying  from  one- 
half  the  weight  of  fat  to  equal  weights  of  the  two. 

The  process  of  making  cold  soap  consists  in  melting 
the  fat,  stirring  in  the  dissolved  caustic  soda  until  a 
homogeneous,  creamy  mass  is  obtained,  and  setting  the 
mixture  aside  in  molds  to  complete  the  saponification 
and  harden.  Twenty-four  hours  usually  suffices.  Some 
household  recipes  are  appended,  made  on  the  basis  of 
i  pound  of  fat.  To  obviate  weighing  1/7  of  a  pound  of 
the  alkali,  it  is  convenient  to  dissolve  a  pound  in  the  right 
amount  of  water,  and  measure  out  the  particular  quantity 
required. 

Laundry  Soap. — 1/7  pound  NaOH  dissolved  in  suffi- 
cient water  to  make  14  fluid  ounces  (i7/8  cups).  Strength 
17°  Baume. 

i  pound  solid  fat  melted. 


2O8  HOUSEHOLD   CHEMISTRY 

Emulsion  Soap. — Add  to  the  above  before  it  hardens, 
3  tablespoon fuls  each  of  kerosene  and  a  strong  solution 
of  washing  soda.  Stir  about  5  minutes  longer.  Incor- 
porate i  pint  of  water  for  a  soft  soap. 

Castile. — 1/7  pound  NaOH  made  up  to  1/2  cup  with 
water.     (38°  Baume.) 
i  pound  olive  oil. 

Coconut  Oil. — ]/<•>  pound  (full  weight)  NaOH  made  up 
to  i  cup. 

i  pound  coconut  oil. 

(The  exact  proportions  are  5^2  pounds  oil  to  i  pound 
NaOH.) 

By  stirring  in  air  with  an  egg  beater,  the  result  will  be 
floating  soap. 

Palm,  Oil. — Y7  pound  NaOH  made  up  to  il/t  cups, 
i  pound  palm  oil. 

Special  Varieties — Scouring  Soaps. — These  are  made 
by  introducing  into  the  soap  while  in  a  creamy  condition, 
a  large  amount  of  finely  pulverized  quartz  or  other  min- 
eral matter. 

Transparent  Soaps. — Such  soaps  are  made  by  incor- 
porating the  amount  of  alcohol  required  to  hold  the  soap 
in  a  clear  solid  solution.  In  some  cases  the  transparency 
is  produced  by  the  use  of  sugar,  which  must  be  consid- 
ered an  adulterant. 

Liquid  soaps  are  soap  solutions  containing  an  excess 
of  the  solvent. 


HOUSEHOLD   CHEMISTRY  2OQ 

Soap  Analysis. — For  detailed  methods,  see  Chapter 
XVI.  As  a  simple  means  of  determining  whether  a  soap 
is  superfatted  or  contains  excess  alkali,  apply  the  follow- 
ing tests : 

TESTS. 

For  Free  Fat. — Shake  a  few  shavings  of  the  soap  in  a  corked 
test  tube  with  cold  gasoline,  filter  into  a  convex  glass  and 
evaporate  the  gasoline  over  warm  water.  A  greasy  residue 
indicates  unsaponified  fat. 

For  Free  Alkali* — Shake  a  few  shavings  of  the  soap  in  a 
corked  test  tube  with  warm  alcohol  (95  per  cent.),  filter  and 
add  to  the  clear  liquid  a  few  drops  of  phenolphthalein ;  a  red 
color  indicates  free  alkali.  Or,  drop  some  of  an  alcoholic  solu- 
tion of  phenolphthalein  on  the  freshly  cut  surface  of  the  soap. 

Scouring  Powders. — These  are  improved  forms  of  the 
old  crude  mixtures  of  sand  and  soap,  formerly  used  ex- 
tensively for  rough  cleaning.  They  now  consist  of  clay, 
incorporated  for  absorbent  purposes,  and  pulverized 
soap,  containing  abrasive  material  in  a  more  or  less  finely 
divided  condition.  Borax  may  be  present,  and  at  times 
clay  is  partly  or  entirely  replaced  by  chalk.  The  common 
fault  with  such  preparations  is  that  their  use  is  recom- 
mended for  general  cleaning,  but  they  frequently  contain 
sharp  abrasive  particles  which  make  them  injurious  to 
fine  metal  or  porcelain  surfaces. 

Average  analyses  of  these  powders  are  appended : 

Per  cent. 

Water   i—  6 

Soap 4 — 14 

Sodium  carbonate o — 24 

Abrasive  material 63 — 93 


2IO  HOUSEHOLD   CHEMISTRY 

Metal  Polishes. — These  polishing  agents  are  on  the 
market  in  liquid,  paste,  and  powder  forms,  also  as  polish- 
ing cloths.  Their  action  in  removing  tarnishes — oxide, 
sulphide  or  carbonate  coatings — depends  upon  the  ab- 
rasive effect  of  pulverized  mineral  material,  the  solvent 
action  of  chemicals,  or  both  combined. 

The  liquid  polishes  are  solutions  containing  as  a  rule 
one  or  more  of  the  following  ingredients :  oxalic  acid, 
muriatic  acid,  ammonia,  benzine  or  benzene,  and  potas- 
sium cyanide.  These  may  be  combined  with  pulverized 
mineral  matter. 

Oxalic  acid  is  very  effective  in  dissolving  metallic 
oxides  and  carbonates,  and  is  therefore  in  common  use  as 
a  cleanser  for  brass  and  other  metals.  The  acid  potassium 
oxalates  are  similarly  used.  The  metal  itself  is  liable 
to  be  attacked  by  oxalic  acid,  which  should  not  be  used 
in  too  strong  solution  for  nickel-plated  faucets,  etc. 

The  cleansing  effect  of  muriatic  acid  is  similar  to  that 
of  oxalic,  and  can  be  produced  in  the  household  by 
using  a  mixture  of  salt  and  vinegar. 

Ammonia  is  an  excellent  cleanser  for  copper  and  brass, 
but  like  all  chemical  solvents  for  tarnishes,  should  be 
removed  by  washing  as  soon  as  the  metal  is  clean. 

Benzine  and  aromatic  benzene  are  valuable  constitu- 
ents of  liquid  polishes,  since  they  act  as  general  solvents. 

Potassium  cyanide  is  used  in  the  trade,  but  as  it  is 
a  violent  poison  its  use  is  unadvisable  in  the  home. 

Pastes. — These  contain  pulverized  mineral  material 
made  into  paste  form  with  soap,  and  in  some  cases  small 


HOUSEHOLD   CHEMISTRY  211 

amounts  of  oxalic  acid,  glycerol,  or  a  hydrocarbon.  Their 
action  is  principally  abrasive,  and  the  mineral  substances 
they  contain  are  those  found  in  the  cleaning  powders 
described  below. 

Powders. — Efficient  polishing  powders  are  whiting, 
clay,  rouge,  talc,  quartz,  emery,  and  silica. 

Whiting  is  finely  pulverized  chalk.  It  costs  about  10 
cents  per  pound,  and  is  useful  for  cleaning  silver,  nickel, 
porcelain,  and  glass.  A  mixture  of  whiting  with  water 
or  alcohol  is  effective  for  window  cleaning.  One  of  the 
scouring  preparations  on  the  market  is  essentially  a 
mixture  of  whiting  and  soap. 

Clay  is  of  varied  character  and  comes  under  different 
names — Tripoli,  rottenstone,  etc.  These  substances  cost 
about  40  cents  per  pound,  and  when  in  finely  divided  con- 
dition are  used  for  general  metal  cleaning.  Rottenstone 
is  frequently  mixed  with  kerosene  for  this  purpose. 

Rouge  is  preferred  by  jewelers  for  polishing  gold  and 
silver,  brass  and  copper.  Jeweler's  rouge  is  finely  pul- 
verized red  oxide  of  iron,  prepared  by  a  special  process, 
and  costs  about  5  cents  per  ounce.  When  mixed  with 
water  it  will  adhere  to  the  surface  on  which  it  is  rubbed. 
Some  of  the  best  metal  polishes  on  the  market  are  com- 
binations of  rouge,  oxalic  acid,  and  a  hydrocarbon. 

Talc  is  pulverized  magnesium  silicate,  and  makes  a 
good  polishing  agent  without  danger  of  scratching. 

Silica,  quarts  and  emery  come  in  different  forms,  as 
knife  brick,  scouring  soaps,  etc.,  and  are  especially  suited 
to  the  polishing  of  steel  and  iron. 


212  HOUSEHOLD   CHEMISTRY 

Polishing  Cloths  are  made  usually  by  impregnating 
soft  durable  fabrics  with  rouge,  talc,  rottenstone  or 
whiting.  A  polishing  cloth  may  be  made  at  home  by 
dipping  a  pile  fabric  or  a  piece  of  chamois  into  fouge 
mixed  with  water  or  alcohol,  and  drying.  Some  of  these 
cloths  have  no  mineral  constituent,  but  polish  by  means 
of  the  fabric  itself. 

TESTS  FOR  CLEANING  AGENTSL 

Oxalic  Acid  or  Oxalates. — Make  a  water  solution,  filter,  add 
Ca(OH)2  to  filtrate.  White  precipitate  of  calcium  oxalate 
appears. 

Benzine  or  Benzene. — Odor  and  inflammability. 

Ammonia. — Odor  and  litmus  test. 

Potassium  Cyanide. — Treat  with  fixed  alkali,  FeSO4,  FeCls  and 
HC1  in  order  given.  Prussian  blue  color. 

Whiting. — Add  CHaCOOH.  An  effervescence  indicates  a  car- 
bonate. Make  test  for  calcium. 

Rouge. — Treat  with  boiling  HC1  (cone.).  If  rouge  is  present, 
it  will  dissolve.  Make  iron  test  with  NH4SCN. 

Clay. — Will  remain  insoluble  when  treated  with  water  or  acid. 

Bleaches,  Grease  and  Stain  Removers. — Many  pro- 
prietary compounds  are  sold  for  these  purposes.  On  an- 
alysis, the  bleaches  are  generally  found  to  be  calcium 
hypochlorite,  Javelle  water,  hydrogen  and  sodium  per- 
oxides, oxalic  acid,  or  potassium  permanganate,  alone  or 
in  combination.  Some  description  of  the  use  and  effect 
of  these  compounds  is  given  in  Chapter  XIV.  If  the 
kind  of  bleach  required  is  known,  it  can  be  bought 
directly,  and  at  less  expense  than  if  purchased  under  its 
proprietary  name.  For  example,  ink  eradicators  usually 
consist  of  Javelle  water  or  a  solution  of  bleaching 


HOUSEHOLD   CHEMISTRY  213 

powder,  accompanied  by  an  acid — oxalic,  muriatic,  or 
citric — the  two  being  combined  at  the  time  of  application. 
The  non-inflammable  solvents  for  grease,  familiar  to 
the  public,  have  for  the  most  part  carbon  tetrachloride 
as  their  principal  ingredient,  with  varying  combinations 
of  benzine  or  gasoline,  benzene,  acetone,  or  chloroform. 
They  have  a  great  advantage  as  to  safety  over  the  danger- 
ous gasoline  or  benzine,  often  used  carelessly  in  the 
home.  These  grease  solvents  will  remove  fresh  paint  or 
varnish  stains,  .since  they  attack  the  fatty  constituent  in 
the  compound.  Turpentine  or  amylacetate  also  soften 
and  dissolve  dried  paint  and  varnish. 

Bluings. — The  character  of  the  bluing  used  in  the  laun- 
dry is  of  importance  to  the  housewife.  The  three  types 
in  common  use — solid,  liquid,  and  aniline  blues — are 
markedly  different  in  properties. 

Solid  blues  are  now  commercially  prepared  ultramarine 
blues,  the  former  type,  indigo  blue,  being  little  used  at 
present.  Ultramarine  is  found  in  nature  in  small  quan- 
tities as  lapis  lazuli ;  as  manufactured,  it  is  a  mixture  of 
sodium  and  aluminium  silicates,  and  sodium  sulphide.  It 
is  characterized  by  insolubility  in  water,  but  the  suspen- 
sion of  its  fine  particles  in  the  bluing  water  gives  a  good 
blue  color.  Unfortunately,  unless  care  is  used,  larger 
particles  sometimes  settle  on  the  clothes,  and  produce 
blue  spots. 

TEST. 

Ultramarine  blue  is  decolorized  on  addition  of  HC1  or  H2SO4. 
Sulphur  is  precipitated  and  H2S  evolved. 


214  HOUSEHOLD   CHEMISTRY 

Liquid  Blues. — These  are  principally  Prussian  blue, 
i.  e.,  Fe4[Fe(Cn)e]8.  Prussian  blue  decomposes  in  the 
presence  of  an  alkali,  such  as  caustic  soda,  and  gives  a 
brown  residue  of  ferric  hydroxide.  This  may  happen 
if  soap  is  carried  over  into  the  bluing  water.  In  that 
case  the  ferric  hydroxide  becomes  iron  rust  on  the 
clothes,  when  the  hot  iron  is  applied. 

TEST. 

Warm  the  sample  of  liquid  bluing  with  NaOH.  A  brown 
precipitate  appears  if  the  bluing  has  an  iron  base.  Filter,  dis- 
solve residue  in  hot  dilute  HC1  and  make  test  for  ferric  com- 
pound, with  NH4SCN. 

Aniline  Blues. — These  are  used  less  in  the  household 
than  in  commercial  laundries,  but  can  be  procured  in 
powder  form  at  a  laundry  supply  establishment.  They 
are  cheaper  than  other  forms  of  bluings,  as  i  ounce  of 
the  powder  will  make  a  strong  solution  in  a  gallon  of 
water.  Acids  are  used  in  most  laundries  for  the  best 
development  of  the  color  on  the  clothes.  If  an  acid  is 
used,  it  should  be  acetic,  which  is  volatile  and  harmless, 
rather  than  oxalic,  which  is  destructive  to  most  fabrics. 

TEST. 

Aniline  blues  slowly  lose  color  in  the  presence  of  caustic  soda. 


CHAPTER  XVI. 


VOLUMETRIC  AND  GRAVIMETRIC  ANALYSIS. 

Normal  Solutions. — The  basis  of  volumetric  analysis  is 
the  normal  solution.  A  normal  solution  is  one  which 
contains  the  hydrogen  equivalent  of  the  substance  in 
grams,  in  I  liter  of  solution.  For  all  monobasic  acids 
and  alkalies  the  hydrogen  equivalent  corresponds  with 
the  molecular  weight  of  the  compounds;  for  dibasic  sub- 
stances it  is  one-half  of  the  molecular  weight.  In  sim- 
ilar manner  tri-  and  tetrabasic  bodies  have  hydrogen 
equivalents  corresponding  to  one-third  and  one-quarter 
of  their  molecular  weight.  To  find  the  equivalent  of  a 
salt,  refer  back  to  the  acid  from  which  the  salt  is  made. 
For  example,  Na2CO3  is  the  sodium  salt  of  H2CO3, 
therefore  it  is  dibasic,  and  its  normal  solution  would 
contain  one-half  its  molecular  weight,  or  53,  in  grams 
per  liter. 

Equal  volumes  of  normal  solutions  of  different  sub- 
stances are  of  equal  strength,  and  equal  volumes  of  nor- 
mal acid  and  alkali  solutions  neutralize  each  other. 

Normal  solutions  may  be  made  one-tenth  or  one- 
hundredth  of  their  full  strength,  either  by  taking  the 
corresponding  fractions  of  their  respective  equivalents 
or  by  diluting  the  full  normal  solutions  proportionately; 
they  are  known  as  deci-  and  centi-normal  solutions  re- 
spectively. 

To  explain  the  preparation  of  the  normal  solutions  of 
acid  and  alkali,  one  example  from  each  class  will  suffice, 


2l6  HOUSEHOLD   CHEMISTRY 

and  as  hydrochloric  acid  and  caustic  soda  have  the  most 
extensive  application,  their  preparation  will  be  given. 

Preparation  of  N/HC1. — The  molecular  weight  of  HC1 
is  36.5,  therefore  36.5  grams  per  liter  are  needed,  but 
as  it  is  a  volatile  liquid  and  cannot  be  weighed  with  any 
accuracy,  it  is  usual  to  calculate  the  volume  of  the  liquid 
from  its  specific  gravity,  and  to  measure  out  the  result 
in  cubic  centimeters,  allowing  a  little  for  loss.  Using 

W 

the  formula  —  =  V,   the  calulation   is  simple  and  is 

made  as  follows:  divide  the  equivalent  in  grams  (36.5) 
by  the  specific  gravity  of  the  concentrated  acid  (1.2); 
this  gives  30.4-4-  as  a  quotient  and  is  the  number  of 
cubic  centimeters  to  be  used  if  the  acid  were  100  per 
cent,  strength,  but  the  strongest  acid  is  only  40  per  cent., 
hence  this  quotient  must  be  multiplied  by  2.5  (30.4  X 
2.5  ,=  76  cc.).  It  is  safe  to  take  78-80  cc.,  adding  it  to 
300  or  400  cc.  of  distilled  water  and  when  cool  diluting 
to  exactly  I  liter. 

The  solution  must  now  be  standardized  against  a  nor- 
mal solution  of  an  alkali  which  can  be  made  exact. 
Sodium  carbonate,  the  equivalent  of  which  is  53,  can  be 
obtained  of  a  high  degree  of  purity  and  may  be  weighed 
exactly.  It  is  hardly  necessary  to  make  up  a  large  quan- 
tity, so  that  5.3  grams  of  pure  dry  soda  are  usually 
weighed  accurately,  dissolved  in  the  least  quantity  of 
water  and  the  resulting  solution  diluted  to  exactly  100 
cc.  at  or  about  60°  F.  This  constitutes  the  exact  normal 
soda,  i  cc.  of  which  contains  5.3  milligrams  of  soda. 


HOUSEHOLD   CHEMISTRY 


Measure  10  cc.  of  the  soda  very  exactly  with  a  pipette, 
run  it  into  a  small  beaker  containing  about  100  cc.  of 
distilled  water  and  add  2  or  3  drops  of  methyl 
orange  solution.  Fill  a  burette  with  the  acid  solution. 
Note  the  level,  and  run  it,  drop  by  drop,  with  constant 
stirring,  into  the  soda.  Stop  when  the  last  drop  changes 
the  color  from  yellow  to  pink  which  remains  even  after 
stirring  for  some  moments.  Read  the  burette  and  note 
the  number  of  cubic  centimeters,  and  fractions  used.  Say 
the  quantity  is  9.8  cc.,  indicating  that  this  quantity  con- 
tains as  much  acid  as  should  exist  in  10  cc.  ;  consequently, 
980  cc.  of  the  liquid  should  be  diluted  to  i  liter.  If 
the  total  amount  of  acid  is  less,  calculate  what  bulk  it 
should  occupy  and  dilute  accordingly.  Continue  the 
titration  until  equal  volumes  of  acid  and  alkali  exactly 
neutralize  each  other. 

The  acid  keeps  well,  but  should  be  preserved  in  tightly 
stoppered  glass  bottles  to  prevent  evaporation. 

Preparation  of  N/NaOH.  —  The  caustic  soda  is  deliques- 
cent and  absorbs  carbon  dioxide,  so  must  be  weighed 
rapidly  and  approximately,  using  rather  more  than  the 
40  grams  required,  say  50  grams.  This  is  dissolved  in 
300  or  400  cc.  of  water,  cooled  and  diluted  to  i  liter. 
Draw  off  10  cc.  of  the  normal  acid  in  a  pipette,  allow  it 
to  run  into  a  small  beaker  containing  about  100  cc.  of 
distilled  water,  and  add  a  few  drops  of  phenolphthalein. 
Fill  a  clean,  dry  burette  with  the  caustic  soda.  Note  its 
level  and  run  it,  drop  by  drop,  with  constant  stirring, 
into  the  acid  solution  until  a  faint  but  distinct  pink  tint 


2l8  HOUSEHOLD   CHEMISTRY 

remains  after  stirring  for  some  moments.  Read  off  the 
quantity  used,  say  9.5  cc.,  showing  the  solution  to  be  too 
strong  and  requiring  dilution  as  in  the  case  of  the  acid. 
After  performing  this  operation  the  acid  and  the  alkali 
should  be  correct  and  I  cc.  of  one  will  exactly  neutralize 
an  equal  quantity  of  the  other. 

Use  of  Indicators. — A  change  in  a  solution  from  acidity 
to  alkalinity,  or  the  reverse,  can  be  shown  by  certain 
color  substances  or  indicators,  sensitive  to  the  slightest 
excess  of  acid  or  alkali.*  The  indicators  in  common  use 
in  acidimetry  and  alkalimetry  are  phenolphthalein  and 
methyl  orange.  The  work  of  an  indicator  may  be  illus- 
trated by  the  action  of  phenolphthalein,  a  weak  acid 
which  undergoes  little  dissociation  in  solution.  In  the 
non-ionized  state  it  is  colorless.  If,  however,  its  acid 
solution  is  neutralized  by  an  alkali,  a  slight  excess  of  the 
alkali  forms  a  salt  of  phenolphthalein  which  ionizes  with 
a  deep  red  color.  A  strong  base  is  necessary  in  order  to 
give  a  sharp  reaction.  Ammonia,  for  instance,  is  too 
weak  a  base  to  ionize  the  weakly  acid  phenolphthalein  in 
dilute  solution.  Phenolphthalein  is  used  most  frequently 
as  an  indicator  for  weak  acids  (excepting  carbonic  and 
hydrosulphuric)  titrated  against  normal  sodium  hydrox- 
ide. 

Methyl  orange,  on  the  other  hand,  is  red  in  its  molecu- 
lar state,  and  changes  to  yellow  on  dissociation.  It  is 
a  moderately  strong  acid,  and  if  added  to  a  basic  solu- 
tion the  salt  formed  is  yellow,  but  the  addition  of  a 
*  For  Theory  of  Indicators,  see  Ostwald:  Foundations  oj 
Analytical  Chemistry,  and  Cairns:  Quantitative  Analysis. 


HOUSEHOLD   CHEMISTRY 


slight  excess  of  a  strong  acid  is  sufficient  to  produce  the 
red  color  of  the  non-ionized  substance.  Its  -reaction 
with  weak  acids  is  not  sharp,  so  its  use  is  not  advised  in 
connection  with  organic  acids.  Because  of  its  strongly 
acid  nature  methyl  orange  is  useful  in  titrating  against 
weak  bases.  It  must  always  be  used  in  cold  solution, 
and  in  small  amounts. 

Congo  red  and  rosolic  acid  are  usually  employed  in 
the  Kjeldahl  determination  of  nitrogen.  The  former  is 
blue  in  acid  solution,  red  in  alkaline.  It  is  dissolved  in 
water  for  use,  and  only  small  amounts  should  be  taken. 
Rosolic  acid  is  yellow  in  the  presence  of  acids;  cherry 
red  with  alkalies.  It  is  dissolved  in  50  per  cent,  alcohol 
for  use. 

To  test  unknown  substances,  first  determine  the  com- 
pound present  by  qualitative  analysis,  and  then  weigh  or 
measure  some  convenient  quantity,  dissolve  or  dilute 
with  distilled  water,  add  the  indicator  and  run  in  the 
acid  or  the  alkali  until  the  neutral  point  is  reached.  Ob- 
serve the  number  of  cubic  centimeters  used,  multiply 
each  by  its  value  in  milligrams  of  the  substance  sought, 
and  divide  the  result  by  the  quantity  used;  multiplying 
this  quotient  by  100  will  yield  per  cent. 

Value  of  i  cc.  of  normal  soda  in  each  of  the  following  : 

Sodium  carbonate  ..........................  0.053 

Acetic  acid   ................................  0.060 

Lactic  acid  .................................  0.090 

Tartaric  acid  ...............................  0.075 

Citric  acid  .................................  0.064 

Hydrochloric  acid   ..........................  0.0365 

15 


220  HOUSEHOLD    CHEMISTRY 

Nitric  acid 0.063 

Sulphuric  acid   0.049 

Potassium  hydroxide  0.056 

Ammonium  hydroxide  0.035 

Calcium  hydroxide  0.037 

For  example,  to  neutralize  10  cc.  of  a  solution  of 
acetic  acid  of  unknown  strength,  8  cc.  of  N/NaOH  are 
required.  The  calculation  would  be: 

i  cc.  N/NaOH  =  0.06  gram  acetic  acid. 

8  cc.  N/NaOH  were  used. 

8  X  0.06  gram  —  0.48  gram  acetic  acid  in  10  cc. 

100  X   (0.48  -f-  10)  =  4.8  grams  acetic  acid  in 

100  cc. 
.'.  the  strength  of  the  acid  is  4.8  per  cent. 

APPLICATIONS  OF  VOLUMETRIC  ANALYSIS. 

Analysis  of  Vinegars — Take  the  specific  gravity  of  the  sample. 
Decolorize  a  portion  (50-100  cc.)  by  passing  it  through  a  bone- 
black  filter,  rejecting  the  first  funnel  full.  Take  10  cc.  of  the 
product,  dilute  with  a  convenient  bulk  of  water  (about  50  cc.), 
add  i  or  2  drops  of  phenolphthalein  as  indicator,  and  titrate 
against  N/NaOH.  Calculate  as  acetic  acid,  using  the  specific 
gravity  of  the  vinegar  to  check  the  resulting  per  cent.  Example : 

Specific  gravity  of  sample  may  be  1.014,  . : .  weight  of  10  cc.  = 
10.14  grams. 

Amount  of  acetic  acid  found  in  10  grams  may  be  0.534  gram. 

•  '•  0.534  -r-  10.14  =  5.26,  the  per  cent,  of  acetic  acid  in  the 
sample. 

To  distinguish  the  source  of  vinegar,  evaporate  10  cc.  to  dry- 
ness,  and  note  the  odor.  Cider  vinegar  will  give  an  odor  suggest- 
ing baked  apples;  malt  vinegar,  a  malt  odor;  distilled  vinegar,  a 
sharp  acid  odor.  Ignite  at  a  low  temperature  to  light-colored 
ash.  In  the  case  of  genuine  cider  or  wine  vinegars  the  quantity 


HOUSEHOLD   CHEMISTRY  221 

of  ash  is  comparatively  large  and  the  reaction  will  be  alkaline. 
Synthetic  vinegar  will  leave  no  appreciable  residue. 

Test  for  Free  Mineral  Acids.* — Dilute  5  cc.  of  the  vinegar 
with  5  to  10  cc.  of  water  to  reduce  the  acidity  to  about  2  per 
cent,  of  acetic  acid,  and  add  4  or  5  drops  of  a  solution  of  methyl 
violet  ( I  part  of  Methyl  Violet  26,  No.  56  of  Bayer  Farbenf abrik, 
Elberfeld,  in  10,000  parts  of  water).  Mineral  acids  change  the 
blue  violet  color  to  a  blue  green  or  green. 

Test  for  Phosphoric  Acid. — Burn  to  ash  in  the  presence  of  a 
few  drops  of  HNOs  and  make  the  usual  test  for  phosphoric  acid. 

Baking  Soda — Test  for  Purity** — Ordinary  baking  soda  may 
contain  some  Na2CO3.  To  determine  the  percentage  of  NaHCO3 
in  the  sample,  dissolve  I  gram  of  commercial  NaHCOs  in  100  cc. 
of  distilled  water,  add  2  drops  of  methyl  orange,  and  titrate 
against  N/ioHaSCX  Since  the  freed  carbonic  acid  is  too  weak 
an  acid  to  produce  the  red  color  with  methyl  orange,  the  latter 
will  give  the  end  point  of  titration  in  this  case  only  when  the 
N/io  HzSO*  has  neutralized  the  total  alkalinity  (combined  as 
mono-  and  bicarbonate)  of  the  soda. 

Now  dissolve  another  gram  of  the  sample  in  250  cc.  of  cold 
water,  add  phenolphthalein,  and  titrate  with  N/io  H2S(X  The 
nose  of  the  burette  should  dip  into  the  solution,  which  should 
be  well  stirred  during  the  titration.  No  carbonic  acid  should 
escape  from  the  liquid  during  the  operation.  Under  suitable 
conditions  of  dilution  and  temperature  the  reaction  is : 

2Na,CO3  +  H2SO4  — *  2NaHCOs  -f  Na2SO4. 

Therefore,  i  cc.  of  half-normal  sulphuric  acid  equals  0.106  grain  of 
Na2CO3  present. 

The  difference  between  the  amounts  of  N/io  acid  used  in  the 
two  titrations  is  the  measure  of  the  bicarbonate  of  soda  in  the 
sample. 

Cream  of  Tartar — Test  for  Purity. — Weigh  i  gram  of  cream 
of  tartar,  add  100  cc.  of  distilled  water,  and  2  drops  of  phenol- 
*  From  Sherman's  Organic  Analysis. 
**  Cairns:  Quantitative  Analysis. 


222  HOUSEHOLD   CHEMISTRY 

phthalein.  Run  in  N/NaOH  until  the  pink  color  comes.  (A 
certain  amount  of  the  alkali  is  necessary  to  the  complete  solution 
of  the  cream  of  tartar.)  Now  add  N/io  HC1  drop  by  drop  until 
the  color  just  disappears,  and  subtract  the  amount  used  from 
the  alkali  in  terms  of  tenth-normal.  The  difference  is  the  amount 
of  NaOH  required  to  neutralize  the  cream  of  tartar.  Calculate 
the  percentage  of  cream  of  tartar  in  the  sample. 

Household  Ammonia. — Take  the  specific  gravity  of  the  sample, 
and  dilute  10  cc.  with  a  convenient  bulk  of  distilled  water.  Add 
2  drops  of  methyl  orange,  and  titrate  against  N/HC1.  Calculate 
percentage  strength,  using  the  specific  gravity  as  a  factor. 

Analysis  of  Soap  or  Soap  Powder — In  a  3-inch  porcelain  dish 
place  1-2  teaspoonfuls  of  clean  dry  sand  and  a  small  glass 
stirring  rod ;  weigh  the  whole.  Add  2-3  grams  of  the  soap 
sample,  finely  shaved,  and  enough  95  per  cent,  alcohol  to  cover 
the  material.  Evaporate  over  a  water  bath,  stirring  meanwhile, 
until  the  alcohol  is  evaporated.  Dry  the  contents  of  the  dish 
in  an  air  bath  at  105°  to  constant  weight.  Estimate  the  loss  in 
weight  as  water. 

Weigh  another  gram  of  the  sample,  finely  shaved,  and 
heat  for  2-2J4  hours  in  an  air  bath,  at  105°.  Treat  the  dried 
material  on  a  hot  water  bath  with  successive  portions  of  hot 
neutral  95  per  cent,  alcohol,  using  about  50  cc.  at  a  time  and 
400-500  cc.  in  all.  Decant  each  portion  of  the  solution  through 
a  balanced  filter  paper,  finally  washing  the  last  portion  through 
the  filter  with  additional  alcohol.  The  combined  filtrates  contain 
the  dissolved  soap ;  the  residue  on  the  filter  paper  is  carbonates, 
chlorides,  borates,  etc.,  and  insoluble  mineral  matter.  Proceed 
with  residue  and  filtrate  as  follows : 

I.  Residue. — Treat  filter  paper  with  boiling  distilled  water  until 
all  trace  of  alkalinity  or  residue  in  the  last  2  or  3  drops  of  the 
filtrate  has  disappeared.  Dry  the  paper  in  the  air  bath  for  about 
an  hour  and  calculate  weight  of  insoluble  material  remaining  on 
it.  Examine  this  under  a  magnifying  lens  for  the  presence  of 
glistening  particles  of  pulverized  quartz,  etc.  Make  up  the  water 
extract  of  the  soluble  material  to  bulk  (e.g.,  500  cc.),  take  100  cc. 


HOUSEHOLD   CHEMISTRY  223 

and  determine  total  alkalinity  by  titrating  against  N/H2SO*. 
Calculate  as  Na2CO3.  In  another  100  cc.  calculate  chlorides  by 
first  exactly  neutralizing  with  dilute  HNOs,  then  titrating  with 
N/io  AgNOs.  Use  potassium  chromate  as  indicator.  Calculate 
that  I  drop  of  N/io  AgNOj  is  equivalent  to  0.000293  gram 
sodium  chloride.  Concentrate  a  third  portion  to  one-tenth  bulk, 
and  make  a  qualitative  test  for  borax  as  follows :  Exactly  neu- 
tralize with  dilute  HC1,  immerse  a  strip  of  freshly  prepared 
turmeric  paper  in  the  liquid,  and  dry  at  warm  water  heat.  Make 
a  second  test  for  borax  on  another  portion,  by  boiling  down 
until  all  of  the  watery  liquid  has  disappeared,  cooling,  adding  a 
mixture  of  equal  parts  of  alcohol  and  glycerol,  and  applying  a 
flame.  If  the  mixture  burns  with  a  yellow  flame  bordered  with 
green,  borax  is  present. 

Evaporate  the  balance  of  the  solution  to  dryness,  heating 
finally  to  110°,  take  up  with  a  little  water  and  a  few  drops  of 
HC1,  and  test  for  sulphates  and  silicates. 

2.  Filtrate. — Heat  on  a  water  bath  until  the  odor  of  alcohol 
has  disappeared,  keeping  the  solution  up  to  full  amount  by 
additions  of  water.  Cool,  bring  solution  up  to  bulk,  and 
determine  free  alkali  (NaOH)  by  titration  against  N/H^SCX 
Then  add  a  known  excess  of  the  normal  acid  (e.g.,  5  cc.),  boil 
until  clear,  add  a  weighed  quantity  (about  5  grams)  of  white 
wax,  and  melt.  Allow  the  mixture  to  stand  undisturbed  until 
the  wax  hardens,  remove  the  cake,  press  it  between  filter  papers 
to  remove  all  moisture,  and  when  dry  weigh.  The  increase  in 
weight  is  due  to  fatty  acids.  Titrate  the  solution  against 
N/NaOH.  The  difference  between  the  5  cc.  of  N/H2SO«  added 
at  the  beginning  and  the  result  now  obtained  gives  the  combined 
alkali.  It  should  amount  to  about  one-seventh  the  weight  of 
the  fatty  acids.  Take  the  sum  of  the  weights  of  combined  alkali 
and  fatty  acids  as  the  measure  of  the  soap  present  in  the 
sample. 

Report  in  percentages  the  findings  of  water,  carbonates, 
chlorides,  free  and  combined  alkali,  fatty  acids,  and  insoluble 
matter. 


224  HOUSEHOLD    CHEMISTRY 

Test  for  Naphtha  Soap — Make  a  strong  water  solution  of  the 
soap  sample  in  a  small  flask,  acidify  slightly  with  diluted  H2SO4, 
and  distill  the  mixture  at  as  low  a  temperature  as  possible.  If 
any  hydrocarbon  is  present  it  will  pass  over  and  condense  with 
the  watery  vapor.  Note  the  odor. 

For  the  detection  of  rosin  or  rosin  oil  in  soap  see  the 
Liebermann-Starch  Reaction,  Sherman's  Organic  Analy- 
sis. 

Analysis  of  a  Cereal. — The  process  consists  in  the  de- 
termination of  water,  ash  constituents,  protein,  fat,  and 
carbohydrate. 

1.  Water. — Dry  1-2  grams  of  the  powdered  cereal  to  constant 
weight,  at  not  over  105°.    Calculate  percentage  of  water,  and  use 
figures  obtained  in  correcting  subsequent  determinations  of  other 
constituents. 

2.  Ash  Constituents. — Ignite  5  grams  of  the  material  in  a  muffle 
furnace  at  the  lowest  possible  heat  to  char  the  material  thor- 
oughly.    Cool,  and  make  hot  water  extract  of  soluble  alkaline 
salts.     Separate  by  filtration  and  evaporate  the  liquid.     Dry  the 
charred  residue  and  ignite  to  white  or  light-colored  ash.     Cool 
and  add  the  water  extract  and  evaporate  to  dryness.     Weigh ; 
the  result  is  total  ash.    Test  the  ash  qualitatively  in  the  ordinary 
manner  for  its  constituents. 

Protein. — Weigh  1-2  grams  of  the  sample,  place  in  a  Kjeldahl 
flask,  add  20  cc.  of  concentrated  sulphuric  acid,  10-12  grams 
of  potassium  sulphate,  and  0.5  gram  of  copper  sulphate.  Partly 
close  the  neck  of  the  flask  with  a  small  funnel  for  purposes 
of  condensation,  and  heat  under  a  hood,  gently  at  first  and 
then  strongly,  until  the  mixture  is  colorless.  It  is  well  to  con- 
tinue heating  for  15-30  minutes  after  this  stage  is  reached.  The 
nitrogenous  matter  in  the  cereal  has  been  converted  into  ammo- 
nium sulphate  by  the  acid  of  the  sulphuric  acid.  The  process 
now  consists  in  liberating  ammonia  from  this  by  the  addition  of 


HOUSEHOLD    CHEMISTRY  22  ^ 

caustic  soda,  distilling  the  free  ammonia  into  a  known  amount 
of  sulphuric  acid,  and  calculating  the  amount  of  nitrogen  present. 

Proceed  by  cooling  the  material  in  the  Kjeldahl  flask,  adding 
about  250  cc.  of  distilled  water,  and  after  the  solid  matter  has 
dissolved,  4  or  5  drops  of  rosolic  acid.  Put  100  cc.  of  N/io 
H2SO4  and  a  few  drops  of  Congo  red  in  an  Erlenmeyer  receiv- 
ing flask,  and  arrange  to  connect  distilling  and  receiving  flasks 
with  a  water  condenser.  The  delivery  tube  of  the  condenser 
should  reach  below  the  acid  in  the  receiving  flask.  Place  small 
pieces  of  zinc  and  paraffin  in  the  Kjeldahl  flask  to  prevent  bump- 
ing, add  80  cc.  or  more  of  caustic  soda  (about  38°  Be.)  and 
connect  up  at  once.  Distill  over  a  low  flame  at  first,  later  increase 
the  heat,  until  about  half  the  contents  of  the  flask  have  passed 
over.  If  the  color  in  the  receiving  flask  becomes  red,  showing 
an  excess  of  ammonia,  quickly  add  a  measured  additional  amount 
of  the  N/io  H2SOi.  Titrate  the  excess  of  acid  in  the  flask 
against  N/io  NaOH  and  calculate  that  i  cc.  of  N/io  H2SO4  is 
the  equivalent  of  0.0014  gram  nitrogen.  As  the  average  per- 
centage of  nitrogen  in  protein  material  is  approximately  16,  the 
grams  of  nitrogen  found  multiplied  by  the  factor  6.25  will  give 
the  amount  of  protein  in  the  sample.* 

Fat. — Weigh  1-2  grams  of  the  air-dried,  pulverized  material, 
place  in  an  extraction  thimble,  and  introduce  into  a  Soxhlet 
or  other  approved  form  of  extraction  apparatus.  Extract  with 
a  pure  form  of  ether  into  a  tared  flask.  The  duration  of  the 
extraction  depends  on  the  character  of  the  material,  but  16  to 
24  hours  are  usually  allowed. 

Remove  the  flask,  evaporate  the  ether,  weigh,  and  calculate 
amount  of  extract. 

Carbohydrate. — Determine  carbohydrate  by  difference.  If  the 
cereal  has  a  notable  amount  of  soluble  carbohydrate,  make  a 
water  extract,  invert  and  estimate  reducing  sugar,  and  determine 
the  insoluble  carbohydrate  by  difference.  Use  the  following 
method : 

*  For  modifications  of  the  Kjeldahl  method  see  Sherman: 
Organic  Analysis. 


226  HOUSEHOLD   CHEMISTRY 

Estimation  of  Reducing  Sugars.— Mix  15  cc.  of  Fehling's  solu- 
tion A  with  the  same  amount  of  Solution  B  in  an  Erlenmeyer 
flask  of  about  250-300  cc.  capacity,  add  about  50  cc.  of  freshly 
boiled  distilled  water,  and  heat  in  boiling  water  for  5  minutes. 
Measure  with  a  pipette  25  cc.  of  the  sugar  solution,  which  should 
be  of  such  a  strength  as  not  to  contain  more  than  0.5  gram  of 
reducing  sugar.  Add  this  to  the  Fehling's  mixture  and  place 
the  flask  in  boiling  water  for  15  minutes.  Remove,  filter  at 
once  with  the  aid  of  moderate  suction  through  a  Gooch  crucible 
prepared  with  asbestos.*  If  the  filtrate  is  not  distinctly  blue, 
showing  that  an  excess  of  Fehling's  has  been  used,  the  operation 
must  be  repeated  with  a  more  dilute  solution  of  the  reducing 
sugar.  Wash  the  precipitate  of  cuprous  oxide  with  boiling  dis- 
tilled water  until  the  filtrate  is  no  longer  alkaline.  The  cuprous 
oxide  can  now  be  (i)  washed  with  alcohol  and  then  with  ether, 
dried  in  an  air  bath  at  100°  for  20  minutes,  weighed  as  cuprous 
oxide,  and  calculated  to  its  cupric  oxide  equivalent.  The  cor- 
responding weight  of  reducing  sugar  may  then  be  determined  by 
referring  to  Defren's  table  (see  Sherman:  Organic  Analysis). 

*To  prepare  the  Gooch  crucible  for  gravimetric  determina- 
tion of  cuprous  oxide,  proceed  as  follows :  Boil  a  good  quality 
of  asbestos  with  nitric  acid  (specific  gravity  1.05  to  i.io),  wash 
with  water,  boil  with  25  per  cent,  sodium  hydroxide,  wash,  and 
repeat  the  treatment.  Finally  stir  the  washed  asbestos  with 
water,  pour  some  into  a  Gooch  crucible,  and  draw  it  into  place 
with  moderate  suction.  When  a  tight  felt  about  i  centimeter 
thick  has  been  laid  down,  ignite  to  constant  weight  and  record 
weight  of  crucible  and  asbestos.  Test  by  running  through  it  a 
"blank"  of  hot  alkaline  Fehling's  solution  and  washing  with 
water  as  in  a  regular  determination.  The  loss  in  weight  should 
not  exceed  J/2  milligram.  If  it  does,  the  filter  is  again  treated 
with  acid  and  alkali  until  it  ceases  to  lose  in  weight.  The 
crucible  may  be  used  for  successive  determinations  by  dissolv- 
ing the  precipitate  each  time  with  nitric  acid,  washing,  igniting  to 
constant  weight. 


HOUSEHOLD   CHEMISTRY 


Or  (2)  the  cuprous  oxide  may  be  ignited  and  weighed  as  cupric 
oxide  and  the  corresponding  amount  of  reducing  sugar  found 
as  before.  A  third  method  consists  in  determining  the  copper 
by  electrolysis  (see  Allihn's  method  and  table  for  the  determina- 
tion of  dextrose). 


CHAPTER  XVII. 


REAGENTS. 


Laboratory  strength 


Commercial 
forms 

Sp.  gr. 

Per 

cent. 

Concentrated 

Sp.  gr. 

Dilute 

Sp.gr. 

Vols. 
H2O 

Vols. 
acid 

Acids 
HC1    

1.2 

1.4 
1.84 

1.06 
0.9 

40 

70 
94 
5° 

28 

full  strength 

Vols.     Vols. 
H..O       acid 

I             I 
full  strength 
full  strength 

full  strength 
20  per  cent. 
20  per  cent. 

dry 

dry 

dry 
dry 

1.2 

1.2 
1.84 
1.  06 

i-3 
1.23 

I 
3 

7 

10 

Vols. 
H2O 

I 

10  per 
10  per 

10  per 
roper 
satui 
satui 
roper 
satui 
5  per 
satui 
satui 
satui 
20  per 
5  per 
10  per 
10  per 

I 

I 

I 
I 

Vols. 
allc. 

I 
cent, 
cent. 

cent, 
cent, 
•ated 
•ated 
cent, 
•ated 
cent, 
•ated 
•ated 
ated 
cent, 
cent, 
cent, 
cent. 

I.I 

I.I 
I.I 
1.007 

o-945 
1.14 
i.i 

i.i 

1.2 

HNO. 

H2SO4   

CH3COOH  . 

Alkalies 
NH4OH  .... 
NaOH  

KOH  

Salts 
NajCO,    .... 
BaCl2  

(NH4)2C,04. 
NasHPO4  •  •  • 
NH4C1  
(NH4)2S04  . 
NH4SCN  ... 
Nad    

MgS04.    ... 
HeCL,  • 

"e*-  ? 
Tannm    

AgN03  

Co(N03)2   .. 
K4Fe(CN)6  . 

Special  Reagents. 

Ammonium  Molybdate,  (NH4)2MoO4. 

Dissolve  100  grams  MoO3  in  200  cc.  strong  NH4OH 


HOUSEHOLD   CHEMISTRY  22Q 

and  200  cc.  H2O;  slowly  pour  resulting  solution  in  1,500 
cc.  HNO3  specific  gravity  1.2. 

Magnesia  Mixture. 

i  gram  MgSO4  or  MgCl2,  i  gram  NH4C1,  4  cc.  am- 
monia, 8  cc.  water. 

Milton's  Reagent. — 100  grams  mercury  dissolved  in 
71.5-72  cc.  HNO3  specific  gravity  1.4  in  the  cold,  when 
action  ceases  add  twice  the  volume  of  cold  water. 

Fehling's  Reagent. — Solution  A — 34.64  grams  CuSO4, 
5H2O  in  400  cc.  of  cold  water,  when  dissolved  make  up 
to  500  cc. 

Solution  B — 50  grams  NaOH  -f-  180  grams  NaKC4 
H4O6  in  300  cc.  of  water,  when  dissolved  and  cooled 
make  up  to  500  cc. 

For  use  mix  equal  volumes  of  A  and  B  and  add  two 
volumes  of  water. 

Bar  feed's  Reagent. — 4.0  grams  copper  acetate,  100  cc. 
water,  2  cc.  acetic  acid. 

Ny lander's  Reagent. — Two  grams  bismuth  sub- 
nitrate,  (BiONO3),  and  4  grams  of  Rochelle  salt, 
(NaKC4H4O6),  in  100  cc.  of  8  per  cent.  NaOH,  specific 
gravity  1.08. 

Nessler's  Reagent. — 35  grams  of  KI  and  13  grams  of 
HgCl2  in  800  cc.  H2O.  Heat  below  boiling  until  dis- 
solved, add  immediately  a  cold  saturated  solution  of 
HgCl2  until  the  red  precipitate  fails  to  dissolve  after 
stirring.  Cool  and  add  160  grams  KOH  dissolved  in  as 
little  water  as  possible,  and  make  up  to  i  liter.  After 
standing  24  hours  pour  off  the  clear  liquid  and  reserve 


23O  HOUSEHOLD   CHEMISTRY 

for  use.  If  necessary,  add  a  little  more  (3 — 5cc.)  HgCl2 
to  increase  the  sensitiveness.  When  properly  prepared, 
the  solution  has  a  pale  yellow  color. 

Cries' s  Reagent  for  Nitrites. — Dissolve  i  gram  of  sul- 
phanilic  acid  in  300  cc.  of  acetic  acid  specific  gravity 
1.04  (30  per  cent). 

Boil  0.2  gram  of  a-naphthylamine  in  400  cc.  of  dis- 
tilled water,  filter  through  a  plug  of  washed  absorbent 
cotton  and  add  360  cc.  of  acetic  acid  (30  per  cent.). 

To  dilute  50  per  cent,  acid  to  30  per  cent.,  take  ^  of 
100  or  60  cc.  of  acid  and  dilute  to  100  cc. 

Basic  Acetate  of  (Sugar  of)  Lead  Solution. — Boil  232 
grams  of  lead  acetate  and  132  grams  of  litharge  (PbO) 
in  750  cc.  of  distilled  water  for  half  an  hour,  cool  dilute 
to  one  liter.  Allow  liquid  to  stand  until  clear  and  decant. 
Specific  gravity  of  solution  should  be  about  1.267. 

Alumina  Cream  for  Clarifying  Syrups,  Etc. — Precipi- 
tate a  solution  of  alum  with  slight  excess  of  ammonia, 
wash  by  decantation  or  filtration  until  neutral  and  sus- 
pend in  water  to  a  creamy  consistency. 

Meta  Phosphoric  Acid. — Dissolve  glacial  phosphoric 
acid  (HPO3)  or  phosphoric  anhydride,  P2O5,  in  ice  and 
water.  As  the  solution  rapidly  changes  to  H3PO4  make 
it  fresh  for  each  day's  work. 

Alcohol. — 95  per  cent,  is  always  acid,  neutralize  with 
dilute  alkali  before  using.  Alcohol  may  readily  be  recov- 
ered from  solutions  and  wash  liquids  by  distilling  over 
hot  water  at  78°-8o°. 


HOUSEHOLD   CHEMISTRY  23! 

Ammonium  Sulphide. — Mix  equal  volumes  of  dis- 
tilled water  and  strong  ammonia  (specific  gravity  0.9)  ; 
divide  the  resulting  solution  in  equal  parts.  Pass  a  cur- 
rent of  H2S  through  one-half  the  solution  until  saturated 
and  then  add  the  balance  of  the  dilute  ammonia. 

Alkaline  Pyrogallol. — Dissolve  20  grams  of  the  best 
pyrogallol  in  100  cc.  of  cooled  freshly  boiled  distilled 
water,  add  0.5  cc.  of  concentrated  H2SO4.  This  solution 
keeps  well. 

For  use  take  enough  of  the  above  and  make  strongly 
alkaline  with  10  per  cent.  NaOH.  Avoid  contact  with 
air  and  use  immediately. 

Alkaline  Potassium  Permanganate. — 8  grams  of  crys- 
tallized potassium  permanganate  with  200  grams  of 
caustic  potash  or  a  corresponding  amount  of  caustic 
soda,  in  I  liter  of  water. 

Acidified  Potassium  Permanganate. — 0.395  gram 
potassium  permanganate  in  I  liter  of  water.  Add  10  cc. 
of  H2SO4  before  using. 

Alcoholic  Potash. — 56  grams  KOH  in  i  liter  95  per 
cent,  alcohol. 

Molisch's  Reagent. — Make  a  15-20  per  cent,  alcoholic 
solution  of  alpha-naphthol.  Use  with  H2SO4  as  directed. 

Schweitzer's  Reagent. — Dissolve  5  grams  of  copper  sul- 
phate in  loo  cc.  of  boiling  water,  add  caustic  soda  solu- 
tion until  the  cupric  hydroxide  is  completely  precipitated, 
wash  the  precipitate  well  and  dissolve  in  the  least  quan- 
tity of  20  per  cent.  NH4OH  (3  volumes  ammonia  specific 
gravity  0.9  -f-  i  volume  H2O  =  20  per  cent.). 


APPENDIX. 


Useful  Tables  and  Equivalents. 


Per  cent. 

Sp.  Gr. 

Degrees  B£. 

H  SO 

XljOV^4      • 

HC1    . 

9-584 
93.5  (cone.) 

i  124 

1.  066 
1-835 

9 
66 

10.17 

1.05 

7 

20.00 

I.I027 

13-5 

NaOH  

40.55 

I  2 

1.2033 

24-5 

10.  06 
11.84 

1.1x6 

1.134 

15 
17 

20.59 
24.81 
32.47 

1.231 
1.274 
J-357 

27 

$ 

1  grain  = 

28.35  grams 

453-6    grams 

i  kilogram 

i teaspoon 

i  tablespoon 

i  cup 

2  cups 
i  liter 
i  inch 
i  foot 


I5-432  grams 
0-0353  02. 
0.0022  Ib. 

I  oz. 
lib. 

2.2  Ibs. 

5  cc. 

15  cc. 

1 6  tablespoons 
i  pint 

1.057  qt.  (U.  S.) 

2.54  cm.  or  0.0254  meter 
30.48  cm.  or  0.3048  meter 


Method  of  changing  from  a  stronger  to  a  weaker  solu- 


HOUSEHOLD   CHEMISTRY 


233 


tion,  e.  g.,  from  acetic  acid  of  50  per  cent,  strength  to  20 
per  cent. : 

20  per  cent.  :  50  per  cent.  :  :  100  cc.  :  x  cc. 
x  =  250  cc. 

Therefore  make  up  100  cc.  of  the  50  per  cent,  acetic 
acid  to  250  cc. 

Interchange  of  Centigrade  and  Fahrenheit  degrees : 

F  =  ^-C  +  32  C=  -|-(F-32). 

0  y 

Comparison  of  Fahrenheit  and  Centigrade  degrees: 


Fahr. 

Cent. 

Fahr. 

Cent. 

0 

—17.78 

95 

35-00 

32 

o.oo 

98 

36.67 

40 

4.44 

IOO 

37.78 

41 

5.00 

104 

40.00 

50 

IO.OO 

H3 

45.00 

59 

15-00 

122 

50.00 

65 

18.33 

140 

60.00 

68 

20.00 

145 

62.78 

72 

22.22 

158 

70.00 

77 

25.00 

I67 

75-oo 

80 

26.67 

I78 

80.00 

212 

IOO.OO 

To  convert  degrees  Baume  to  specific  gravity  apply 
the  formulas : 

For  liquids  heavier  than  water — 

144 

144  —  Be0 
For  liquids  lighter  than  water — 


134 


=  specific  gravity. 


List  of  Apparatus  for  Students  in  Household  Chemistry. 


Three  rings   (iron). 
Filter  ring. 
Clamps. 
Triangular  file. 
Round  file. 
Triangles. 
Wire  gauze. 
Steel  forceps. 
Wing-top. 
Horn  spatula. 

Tube   brushes — three    (as- 
sorted sizes). 
Filter  paper. 
Test  tube  holder. 
Scissors. 
Knife. 
Thermometer.     Centigrade 

0°-I20°. 

Glass    rod    with    platinum 
wire. 

Flat  glasses,  4  inch. 
Blue  glass. 
Watch-crystals — four. 


Microscope      slides      with 

cover  glasses — four. 
Test  tubes — i  doz.  6-inch 
Test  tubes —  i  doz.  4-inch. 
Hard-glass  test  tubes  ( i  in. 

X  6  in.) — two. 
Graduates,  10  cc.  25  cc. 
Porcelain    dishes    —    two 

(3#   inch). 
Beakers   (Jaikel   1-4). 
Tripod. 

Test  tube  rack. 
Agate  boilers   with  cover, 

YI  pint. 
4   funnels — two   inch   and 

three  inch. 

Flasks — one  4  oz.  high. 
Flasks — two     4     oz.     low 

(wide  mouth). 
Flask — one    16   oz.    round 

bottom. 

Wash-bottle — 16  oz. 
Wide  mouth  bottle,  8  oz. 
Water-bath,  5  in. 


Food  Industries 

An  Elementary  Text-Book  on  the  Production  and 

Manufacture  of  Staple  Foods 

BY 

HERMANN  N.  T.  VULTE,  Ph.  D.,  F.  C.  S. 

Professor  Household  Arts,  Teachers  College,  Columbia  University 
and 

SADIE  B.  VANDERBILT,  B.S. 

Instructor  Household  Arts,  Teachers  College,  Columbia  University, 
New  York.  N.  Y. 

CONTENTS.—  Introduction.  Chapter  I. — Food  Princi- 
ples. Chapter  II. — Water.  Chapter  III.— The  King  of 
Cereals.  Old  Milling  Processes.  Chapter  IV. — Modern 
Milling  and  Mill  Products.  Chapter  V.  —Cereals.  Chap- 
ter VI. — Breakfast  Foods  and  Coffee  Substitutes.  Chap- 
ter VII. — Utilization  of  Flour.  Breadmaking.  Chapter 
VIII. — Leavening  Agents.  Chapter  IX. — Starch  and 
Allied  Industries.  Chapter  X. — The  Sugar  Industry. 
Chapter  XI. — Alcoholic  Beverages.  Chapter  XII.— Alco- 
holic Beverages  (continued).  Chapter  XIII.— Fats. 
Chapter  XIV  —Animal  Foods.  Chapter  XV.— The  Pack- 
ing House.  Chapter  XVI. —Milk.  Chapter  XVII.— Milk 
Products.  Chapter  XVIII.— Preservation  of  Foods. 
Chapter  XIX.— The  Canning  Industry.  Chapter  XX.— 
Tea  Coffee  and  Coco.  Chapter  XXI. — Spices  and  Condi- 
ments. Bibliography.  Index. 

8vo.     Pages  VIII  +  309.     78  Illustrations. 
Price,  $1.75,  Postpaid. 


A  New  Type  of  College  Education 

OFFERED  BY  THE 

SCHOOL  OF  PRACTICAL  ARTS 
TEACHERS  COLLEGE, 
Columbia    University 


^Q 

The  School  of  Practical  Arts  offers  curricula 
leading  to  the  degree  of  Bachelor  of  Science, 
combining  cultural  and  vocational  training. 
The  usual  college  subjects  such  as  English, 
History,  Modern  Languages  and  Science  are 
supplemented  by  professional  courses  of  col- 
legiate grade  in  one  or  more  of  the  following 
fields:  Fine  Arts,  House  Design  and  Decora- 
tion, Costume  Design  and  Illustration,  Foods 
and  Cookery,  Textiles  and  Clothing,  House-  M 
hold  Administration,  Industrial  Drawing,  Met- 
al  Working,  Wood  Working,  Music,  Physical 
Education  and  Nurses  Education.  Prepara-  M 
tion  for  teaching  any  of  the  above  subjects 
may  be  included. 

Graduate  courses  leading  to  higher  degrees 
with  opportunity  for  specializing  in  the  above 
fields  are  also  ofiered. 

For  full  information  address  the  Secretary 
of  Teachers  College. 


A     000530531     3 


SOUTHERN 

UNIVERSITY  OF  CALIFORNIA, 

LIBRARY, 


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